Bean Integration

Camel supports the integration of beans and POJOs in a number of ways

Annotations

If a bean is defined in Spring XML or scanned using the Spring component scanning mechanism and a <camelContext> is used or a CamelBeanPostProcessor then we process a number of Camel annotations to do various things such as injecting resources or producing, consuming or routing messages.

The following annotations is supported and inject by Camel's CamelBeanPostProcessor

See more details at:

• POJO Consuming to consume and possibly route messages from Camel
• POJO Producing to make it easy to produce camel messages from your POJOs
• DynamicRouter Annotation for creating a Dynamic Router from a POJO method
• RecipientList Annotation for creating a Recipient List from a POJO method
• RoutingSlip Annotation for creating a Routing Slip for a POJO method
• Bean Injection to inject Camel related resources into your POJOs
• Using Exchange Pattern Annotations describes how the pattern annotations can be used to change the behaviour of method invocations with Spring Remoting or POJO Producing

Bean Component

The Bean component allows one to invoke a particular method. Alternately the Bean component supports the creation of a proxy via ProxyHelper to a Java interface; which the implementation just sends a message containing a BeanInvocation to some Camel endpoint.

Spring Remoting

We support a Spring Remoting provider which uses Camel as the underlying transport mechanism. The nice thing about this approach is we can use any of the Camel transport Components to communicate between beans. It also means we can use Content Based Router and the other Enterprise Integration Patterns in between the beans; in particular we can use Message Translator to be able to convert what the on-the-wire messages look like in addition to adding various headers and so forth.

Annotation Based Expression Language

You can also use any of the Languages supported in Camel to bind expressions to method parameters when using Bean Integration. For example you can use any of these annotations:

Example:

public class Foo {
	
    @MessageDriven(uri = "activemq:my.queue")
    public void doSomething(@XPath("/foo/bar/text()") String correlationID, @Body String body) {
		// process the inbound message here
    }
}

Advanced example using @Bean

And an example of using the the @Bean binding annotation, where you can use a POJO where you can do whatever java code you like:

public class Foo {
	
    @MessageDriven(uri = "activemq:my.queue")
    public void doSomething(@Bean("myCorrelationIdGenerator") String correlationID, @Body String body) {
		// process the inbound message here
    }
}

And then we can have a spring bean with the id myCorrelationIdGenerator where we can compute the id.

public class MyIdGenerator {

    private UserManager userManager;

    public String generate(@Header(name = "user") String user, @Body String payload) throws Exception {
       User user = userManager.lookupUser(user);
       String userId = user.getPrimaryId();
       String id = userId + generateHashCodeForPayload(payload);
       return id;
   }
}

The POJO MyIdGenerator has one public method that accepts two parameters. However we have also annotated this one with the @Header and @Body annotation to help Camel know what to bind here from the Message from the Exchange being processed.

Of course this could be simplified a lot if you for instance just have a simple id generator. But we wanted to demonstrate that you can use the Bean Binding annotations anywhere.

public class MySimpleIdGenerator {

    public static int generate()  {
       // generate a unique id
       return 123;
   }
}

And finally we just need to remember to have our bean registered in the Spring Registry:

   <bean id="myCorrelationIdGenerator" class="com.mycompany.MySimpleIdGenerator"/>

Example using Groovy

In this example we have an Exchange that has a User object stored in the in header. This User object has methods to get some user information. We want to use Groovy to inject an expression that extracts and concats the fullname of the user into the fullName parameter.

    public void doSomething(@Groovy("$request.header['user'].firstName $request.header['user'].familyName) String fullName, @Body String body) {
		// process the inbound message here
    }

Groovy supports GStrings that is like a template where we can insert $ placeholders that will be evaluated by Groovy.

Bean Binding

Bean Binding in Camel defines both which methods are invoked and also how the Message is converted into the parameters of the method when it is invoked.

Choosing the method to invoke

The binding of a Camel Message to a bean method call can occur in different ways, in the following order of importance:

• if the message contains the header CamelBeanMethodName then that method is invoked, converting the body to the type of the method's argument.
  • From Camel 2.8 onwards you can qualify parameter types to select exactly which method to use among overloads with the same name (see below for more details).
  • From Camel 2.9 onwards you can specify parameter values directly in the method option (see below for more details).
• you can explicitly specify the method name in the DSL or when using POJO Consuming or POJO Producing
• if the bean has a method marked with the @Handler annotation, then that method is selected
• if the bean can be converted to a Processor using the Type Converter mechanism, then this is used to process the message. The ActiveMQ component uses this mechanism to allow any JMS MessageListener to be invoked directly by Camel without having to write any integration glue code. You can use the same mechanism to integrate Camel into any other messaging/remoting frameworks.
• if the body of the message can be converted to a BeanInvocation (the default payload used by the ProxyHelper) component - then that is used to invoke the method and pass its arguments
• otherwise the type of the body is used to find a matching method; an error is thrown if a single method cannot be chosen unambiguously.
• you can also use Exchange as the parameter itself, but then the return type must be void.
• if the bean class is private (or package-private), interface methods will be preferred (from Camel 2.9 onwards) since Camel can't invoke class methods on such beans

In cases where Camel cannot choose a method to invoke, an AmbiguousMethodCallException is thrown.

By default the return value is set on the outbound message body. 

Asynchronous processing

From Camel 2.18 onwards you can return a CompletionStage implementation (e.g. a CompletableFuture) to implement asynchronous processing.

Please be sure to properly complete the CompletionStage with the result or exception, including any timeout handling. Exchange processing would wait for completion and would not impose any timeouts automatically. It's extremely useful to monitor Inflight repository for any hanging messages.

Note that completing with "null" won't set outbody message body to null, but would keep message intact. This is useful to support methods that don't modify exchange and return CompletableFuture<Void>. To set body to null, just add Exchange method parameter and directly modify exchange messages.

Examples:

Simple asynchronous processor, modifying message body.

public CompletableFuture<String> doSomethingAsync(String body)

Composite processor that do not modify exchange

 public CompletableFuture<Void> doSomethingAsync(String body) {
     return CompletableFuture.allOf(doA(body), doB(body), doC()); 
 }

Parameter binding

When a method has been chosen for invocation, Camel will bind to the parameters of the method.

The following Camel-specific types are automatically bound:

• org.apache.camel.Exchange
• org.apache.camel.Message
• org.apache.camel.CamelContext
• org.apache.camel.TypeConverter
• org.apache.camel.spi.Registry
• java.lang.Exception

So, if you declare any of these types, they will be provided by Camel. Note that Exception will bind to the caught exception of the Exchange - so it's often usable if you employ a Pojo to handle, e.g., an onException route.

What is most interesting is that Camel will also try to bind the body of the Exchange to the first parameter of the method signature (albeit not of any of the types above). So if, for instance, we declare a parameter as String body, then Camel will bind the IN body to this type. Camel will also automatically convert to the type declared in the method signature.

Let's review some examples:

Below is a simple method with a body binding. Camel will bind the IN body to the body parameter and convert it to a String.

public String doSomething(String body)

In the following sample we got one of the automatically-bound types as well - for instance, a Registry that we can use to lookup beans.

public String doSomething(String body, Registry registry) 

We can use Exchange as well:

public String doSomething(String body, Exchange exchange) 

You can also have multiple types:

public String doSomething(String body, Exchange exchange, TypeConverter converter) 

And imagine you use a Pojo to handle a given custom exception InvalidOrderException - we can then bind that as well:

public String badOrder(String body, InvalidOrderException invalid) 

Notice that we can bind to it even if we use a sub type of java.lang.Exception as Camel still knows it's an exception and can bind the cause (if any exists).

So what about headers and other stuff? Well now it gets a bit tricky - so we can use annotations to help us, or specify the binding in the method name option.
See the following sections for more detail.

Binding Annotations

You can use the Parameter Binding Annotations to customize how parameter values are created from the Message

Examples

For example, a Bean such as:

public class Bar {
    public String doSomething(String body) {
    // process the in body and return whatever you want 
    return "Bye World"; 
} 

Or the Exchange example. Notice that the return type must be void when there is only a single parameter of the type org.apache.camel.Exchange:

 public class Bar {
     public void doSomething(Exchange exchange) {
         // process the exchange 
         exchange.getIn().setBody("Bye World"); 
 }

@Handler

You can mark a method in your bean with the @Handler annotation to indicate that this method should be used for Bean Binding.
This has an advantage as you need not specify a method name in the Camel route, and therefore do not run into problems after renaming the method in an IDE that can't find all its references.

public class Bar {
    @Handler 
    public String doSomething(String body) {
        // process the in body and return whatever you want 
        return "Bye World"; 
    }
} 

Parameter binding using method option

Available as of Camel 2.9

Camel uses the following rules to determine if it's a parameter value in the method option

• The value is either true or false which denotes a boolean value
• The value is a numeric value such as 123 or 7
• The value is a String enclosed with either single or double quotes
• The value is null which denotes a null value
• It can be evaluated using the Simple language, which means you can use, e.g., body, header.foo and other Simple tokens. Notice the tokens must be enclosed with ${ }.

Any other value is consider to be a type declaration instead - see the next section about specifying types for overloaded methods.

When invoking a Bean you can instruct Camel to invoke a specific method by providing the method name:

.bean(OrderService.class, "doSomething")

Here we tell Camel to invoke the doSomething method - Camel handles the parameters' binding. Now suppose the method has 2 parameters, and the 2nd parameter is a boolean where we want to pass in a true value:

public void doSomething(String payload, boolean highPriority) {
    ... 
}

This is now possible in Camel 2.9 onwards:

.bean(OrderService.class, "doSomething(*, true)") 

In the example above, we defined the first parameter using the wild card symbol *, which tells Camel to bind this parameter to any type, and let Camel figure this out. The 2nd parameter has a fixed value of true. Instead of the wildcard symbol we can instruct Camel to use the message body as shown:

.bean(OrderService.class, "doSomething(${body}, true)") 

The syntax of the parameters is using the Simple expression language so we have to use ${ } placeholders in the body to refer to the message body.

If you want to pass in a null value, then you can explicit define this in the method option as shown below:

.to("bean:orderService?method=doSomething(null, true)")

Specifying null as a parameter value instructs Camel to force passing a null value.

Besides the message body, you can pass in the message headers as a java.util.Map:

.bean(OrderService.class, "doSomethingWithHeaders(${body}, ${headers})") 

You can also pass in other fixed values besides booleans. For example, you can pass in a String and an integer:

.bean(MyBean.class, "echo('World', 5)") 

In the example above, we invoke the echo method with two parameters. The first has the content 'World' (without quotes), and the 2nd has the value of 5.
Camel will automatically convert these values to the parameters' types.

Having the power of the Simple language allows us to bind to message headers and other values such as:

.bean(OrderService.class, "doSomething(${body}, ${header.high})") 

You can also use the OGNL support of the Simple expression language. Now suppose the message body is an object which has a method named asXml. To invoke the asXml method we can do as follows:

.bean(OrderService.class, "doSomething(${body.asXml}, ${header.high})") 

Instead of using .bean as shown in the examples above, you may want to use .to instead as shown:

.to("bean:orderService?method=doSomething(${body.asXml}, ${header.high})") 

Using type qualifiers to select among overloaded methods

Available as of Camel 2.8

If you have a Bean with overloaded methods, you can now specify parameter types in the method name so Camel can match the method you intend to use.
Given the following bean:

 from("direct:start")
    .bean(MyBean.class, "hello(String)")
    .to("mock:result");

Then the MyBean has 2 overloaded methods with the names hello and times. So if we want to use the method which has 2 parameters we can do as follows in the Camel route:

from("direct:start")
    .bean(MyBean.class, "hello(String,String)")
    .to("mock:result"); 

We can also use a * as wildcard so we can just say we want to execute the method with 2 parameters we do

 from("direct:start")
    .bean(MyBean.class, "hello(*,*)")
    .to("mock:result");

By default Camel will match the type name using the simple name, e.g. any leading package name will be disregarded. However if you want to match using the FQN, then specify the FQN type and Camel will leverage that. So if you have a com.foo.MyOrder and you want to match against the FQN, and not the simple name "MyOrder", then follow this example:

.bean(OrderService.class, "doSomething(com.foo.MyOrder)")

Camel currently only supports either specifying parameter binding or type per parameter in the method name option. You cannot specify both at the same time, such as

 doSomething(com.foo.MyOrder ${body}, boolean ${header.high})

This may change in the future.

Bean Injection

We support the injection of various resources using @EndpointInject or @BeanInject. This can be used to inject

• Endpoint instances which can be used for testing when used with Mock endpoints; see the Spring Testing for an example.
• ProducerTemplate instances for POJO Producing
• client side proxies for POJO Producing which is a simple approach to Spring Remoting

Using @BeanInject

From Camel 2.13 onwards you can inject beans (obtained from the Registry) into your beans such as RouteBuilder classes.

For example to inject a bean named foo, you can enlist the bean in the Registry such as in a Spring XML file:

<bean id="foo" class="com.foo.MyFooBean"/>

And then in a Java RouteBuilder class, you can inject the bean using @BeanInject as shown below:

public class MyRouteBuilder extends RouteBuilder {

   @BeanInject("foo")
   MyFooBean foo;

   public void configure() throws Exception {
     ..
   }
}

If you omit the name, then Camel does a lookup by type, and injects the bean if there is exactly only one bean of that type enlisted in the Registry.

   @BeanInject
   MyFooBean foo;

Parameter Binding Annotations

Annotations can be used to define an Expression or to extract various headers, properties or payloads from a Message when invoking a bean method (see Bean Integration for more detail of how to invoke bean methods) together with being useful to help disambiguate which method to invoke.

If no annotations are used then Camel assumes that a single parameter is the body of the message. Camel will then use the Type Converter mechanism to convert from the expression value to the actual type of the parameter.

The core annotations are as follows

The follow annotations @Headers, @OutHeaders and @Properties binds to the backing java.util.Map so you can alter the content of these maps directly, for instance using the put method to add a new entry. See the OrderService class at Exception Clause for such an example. You can use @Header("myHeader") and @Property("myProperty") to access the backing java.util.Map.

Example

In this example below we have a @Consume consumer (like message driven) that consumes JMS messages from the activemq queue. We use the @Header and @Body parameter binding annotations to bind from the JMSMessage to the method parameters.

public class Foo {
	
    @Consume(uri = "activemq:my.queue")
    public void doSomething(@Header("JMSCorrelationID") String correlationID, @Body String body) {
		// process the inbound message here
    }

}

In the above Camel will extract the value of Message.getJMSCorrelationID(), then using the Type Converter to adapt the value to the type of the parameter if required - it will inject the parameter value for the correlationID parameter. Then the payload of the message will be converted to a String and injected into the body parameter.

You don't necessarily need to use the @Consume annotation if you don't want to as you could also make use of the Camel DSL to route to the bean's method as well.

Using the DSL to invoke the bean method

Here is another example which does not use POJO Consuming annotations but instead uses the DSL to route messages to the bean method

public class Foo {
    public void doSomething(@Header("JMSCorrelationID") String correlationID, @Body String body) {
		// process the inbound message here
    }

}

The routing DSL then looks like this

from("activemq:someQueue").
  to("bean:myBean");

Here myBean would be looked up in the Registry (such as JNDI or the Spring ApplicationContext), then the body of the message would be used to try figure out what method to call.

If you want to be explicit you can use

from("activemq:someQueue").
  to("bean:myBean?methodName=doSomething");

And here we have a nifty example for you to show some great power in Camel. You can mix and match the annotations with the normal parameters, so we can have this example with annotations and the Exchange also:

    public void doSomething(@Header("user") String user, @Body String body, Exchange exchange) {
        exchange.getIn().setBody(body + "MyBean");
    }

public class Foo {
	
    @MessageDriven(uri = "activemq:my.queue")
    public void doSomething(@XPath("/foo/bar/text()") String correlationID, @Body String body) {
		// process the inbound message here
    }
}

public class Foo {
	
    @MessageDriven(uri = "activemq:my.queue")
    public void doSomething(@Bean("myCorrelationIdGenerator") String correlationID, @Body String body) {
		// process the inbound message here
    }
}

public class MyIdGenerator {

    private UserManager userManager;

    public String generate(@Header(name = "user") String user, @Body String payload) throws Exception {
       User user = userManager.lookupUser(user);
       String userId = user.getPrimaryId();
       String id = userId + generateHashCodeForPayload(payload);
       return id;
   }
}

public class MySimpleIdGenerator {

    public static int generate()  {
       // generate a unique id
       return 123;
   }
}

   <bean id="myCorrelationIdGenerator" class="com.mycompany.MySimpleIdGenerator"/>

    public void doSomething(@Groovy("$request.header['user'].firstName $request.header['user'].familyName) String fullName, @Body String body) {
		// process the inbound message here
    }

@Consume

To consume a message you use the @Consume annotation to mark a particular method of a bean as being a consumer method. The uri of the annotation defines the Camel Endpoint to consume from.

e.g. lets invoke the onCheese() method with the String body of the inbound JMS message from ActiveMQ on the cheese queue; this will use the Type Converter to convert the JMS ObjectMessage or BytesMessage to a String - or just use a TextMessage from JMS

public class Foo {

  @Consume(uri="activemq:cheese")
  public void onCheese(String name) {
    ...
  }
}

The Bean Binding is then used to convert the inbound Message to the parameter list used to invoke the method .

What this does is basically create a route that looks kinda like this

from(uri).bean(theBean, "methodName");

Using context option to apply only a certain CamelContext

See the warning above.

You can use the context option to specify which CamelContext the consumer should only apply for. For example:

  @Consume(uri="activemq:cheese", context="camel-1")
  public void onCheese(String name) {

The consumer above will only be created for the CamelContext that have the context id = camel-1. You set this id in the XML tag:

<camelContext id="camel-1" ...>

Using an explicit route

If you want to invoke a bean method from many different endpoints or within different complex routes in different circumstances you can just use the normal routing DSL or the Spring XML configuration file.

For example

from(uri).beanRef("myBean", "methodName");

which will then look up in the Registry and find the bean and invoke the given bean name. (You can omit the method name and have Camel figure out the right method based on the method annotations and body type).

Use the Bean endpoint

You can always use the bean endpoint

from(uri).to("bean:myBean?method=methodName");

Using a property to define the endpoint

Available as of Camel 2.11

The following annotations @Consume, @Produce, @EndpointInject, now offers a property attribute you can use to define the endpoint as a property on the bean. Then Camel will use the getter method to access the property.

For example

public class MyService {
  private String serviceEndpoint;
  
  public void setServiceEndpoint(String uri) {
     this.serviceEndpoint = uri;
  }

  public String getServiceEndpoint() {
     return serviceEndpoint
  }

  @Consume(property = "serviceEndpoint")
  public void onService(String input) {
     ...
  }
}

The bean MyService has a property named serviceEndpoint which has getter/setter for the property. Now we want to use the bean for POJO Consuming, and hence why we use @Consume in the onService method. Notice how we use the property = "serviceEndpoint to configure the property that has the endpoint url.

If you define the bean in Spring XML or Blueprint, then you can configure the property as follows:

<bean id="myService" class="com.foo.MyService">
  <property name="serviceEndpoint" value="activemq:queue:foo"/>
</bean>

This allows you to configure the bean using any standard IoC style.

Camel offers a naming convention which allows you to not have to explicit name the property.
Camel uses this algorithm to find the getter method. The method must be a getXXX method.

1. Use the property name if explicit given
2. If no property name was configured, then use the method name
3. Try to get the property with name*Endpoint* (eg with Endpoint as postfix)
4. Try to get the property with the name as is (eg no postfix or postfix)
5. If the property name starts with on then omit that, and try step 3 and 4 again.

So in the example above, we could have defined the @Consume annotation as

  @Consume(property = "service")
  public void onService(String input) {

Now the property is named 'service' which then would match step 3 from the algorithm, and have Camel invoke the getServiceEndpoint method.

We could also have omitted the property attribute, to make it implicit

  @Consume
  public void onService(String input) {

Now Camel matches step 5, and loses the prefix on in the name, and looks for 'service' as the property. And because there is a getServiceEndpoint method, Camel will use that.

Which approach to use?

Using the @Consume annotations are simpler when you are creating a simple route with a single well defined input URI.

However if you require more complex routes or the same bean method needs to be invoked from many places then please use the routing DSL as shown above.

@EndpointInject

To allow sending of messages from POJOs you can use the @EndpointInject annotation. This will inject a ProducerTemplate so that the bean can participate in message exchanges.

Example: send a message to the foo.bar ActiveMQ queue:

public class Foo {
  @EndpointInject(uri="activemq:foo.bar")
  ProducerTemplate producer;

  public void doSomething() {
    if (whatever) {
      producer.sendBody("<hello>world!</hello>");
    }
  }
}

The downside of this is that your code is now dependent on a Camel API, the ProducerTemplate. The next section describes how to remove this dependency.

Hiding the Camel APIs From Your Code Using @Produce

We recommend Hiding Middleware APIs from your application code so the next option might be more suitable. You can add the @Produce annotation to an injection point (a field or property setter) using a ProducerTemplate or using some interface you use in your business logic. Example:

public interface MyListener {
    String sayHello(String name);
}

public class MyBean {
    @Produce(uri = "activemq:foo")
    protected MyListener producer;

    public void doSomething() {
        // lets send a message
        String response = producer.sayHello("James");
    }
}

Here Camel will automatically inject a smart client side proxy at the @Produce annotation - an instance of the MyListener instance. When we invoke methods on this interface the method call is turned into an object and using the Camel Spring Remoting mechanism it is sent to the endpoint - in this case the ActiveMQ endpoint to queue foo; then the caller blocks for a response.

If you want to make asynchronous message sends then use an @InOnly annotation on the injection point.

@RecipientList Annotation

We support the use of @RecipientList on a bean method to easily create a dynamic Recipient List using a Java method.

Simple Example using @Consume and @RecipientList

package com.acme.foo;

public class RouterBean {

    @Consume(uri = "activemq:foo")
    @RecipientList
    public String[] route(String body) {
        return new String[]{"activemq:bar", "activemq:whatnot"};
    }
}

For example if the above bean is configured in Spring when using a <camelContext> element as follows

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="
       http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
       http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring.xsd
    ">

  <camelContext xmlns="http://activemq.apache.org/camel/schema/spring"/>

  <bean id="myRecipientList" class="com.acme.foo.RouterBean"/>

</beans>

then a route will be created consuming from the foo queue on the ActiveMQ component which when a message is received the message will be forwarded to the endpoints defined by the result of this method call - namely the bar and whatnot queues.

How it works

The return value of the @RecipientList method is converted to either a java.util.Collection / java.util.Iterator or array of objects where each element is converted to an Endpoint or a String, or if you are only going to route to a single endpoint then just return either an Endpoint object or an object that can be converted to a String. So the following methods are all valid

@RecipientList 
public String[] route(String body) { ... }

@RecipientList 
public List<String> route(String body) { ... }

@RecipientList 
public Endpoint route(String body) { ... }

@RecipientList 
public Endpoint[] route(String body) { ... }

@RecipientList 
public Collection<Endpoint> route(String body) { ... }

@RecipientList 
public URI route(String body) { ... }

@RecipientList 
public URI[] route(String body) { ... }

Then for each endpoint or URI the message is forwarded a separate copy to that endpoint.

You can then use whatever Java code you wish to figure out what endpoints to route to; for example you can use the Bean Binding annotations to inject parts of the message body or headers or use Expression values on the message.

More Complex Example Using DSL

In this example we will use more complex Bean Binding, plus we will use a separate route to invoke the Recipient List

public class RouterBean2 {

    @RecipientList
    public String route(@Header("customerID") String custID String body) {
    	if (custID == null)  return null;
        return "activemq:Customers.Orders." + custID;
    }
}

public class MyRouteBuilder extends RouteBuilder {
    protected void configure() {
        from("activemq:Orders.Incoming").recipientList(bean("myRouterBean", "route"));
    }
}

Notice how we are injecting some headers or expressions and using them to determine the recipients using Recipient List EIP.
See the Bean Integration for more details.

Using Exchange Pattern Annotations

When working with POJO Producing or Spring Remoting you invoke methods which typically by default are InOut for Request Reply. That is there is an In message and an Out for the result. Typically invoking this operation will be synchronous, the caller will block until the server returns a result.

Camel has flexible Exchange Pattern support - so you can also support the Event Message pattern to use InOnly for asynchronous or one way operations. These are often called 'fire and forget' like sending a JMS message but not waiting for any response.

From 1.5 onwards Camel supports annotations for specifying the message exchange pattern on regular Java methods, classes or interfaces.

Specifying InOnly methods

Typically the default InOut is what most folks want but you can customize to use InOnly using an annotation.

public interface Foo {
  Object someInOutMethod(String input);
  String anotherInOutMethod(Cheese input);
  
  @InOnly
  void someInOnlyMethod(Document input);
}

The above code shows three methods on an interface; the first two use the default InOut mechanism but the someInOnlyMethod uses the InOnly annotation to specify it as being a oneway method call.

Class level annotations

You can also use class level annotations to default all methods in an interface to some pattern such as

@InOnly
public interface Foo {
  void someInOnlyMethod(Document input);
  void anotherInOnlyMethod(String input);
}

Annotations will also be detected on base classes or interfaces. So for example if you created a client side proxy for

public class MyFoo implements Foo {
  ...
}

Then the methods inherited from Foo would be InOnly.

Overloading a class level annotation

You can overload a class level annotation on specific methods. A common use case for this is if you have a class or interface with many InOnly methods but you want to just annote one or two methods as InOut

@InOnly
public interface Foo {
  void someInOnlyMethod(Document input);
  void anotherInOnlyMethod(String input);
  
  @InOut
  String someInOutMethod(String input); 
}

In the above Foo interface the someInOutMethod will be InOut

Using your own annotations

You might want to create your own annotations to represent a group of different bits of metadata; such as combining synchrony, concurrency and transaction behaviour.

So you could annotate your annotation with the @Pattern annotation to default the exchange pattern you wish to use.

For example lets say we want to create our own annotation called @MyAsyncService

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE, ElementType.METHOD})

// lets add the message exchange pattern to it
@Pattern(ExchangePattern.InOnly)

// lets add some other annotations - maybe transaction behaviour?

public @interface MyAsyncService {
}

Now we can use this annotation and Camel will figure out the correct exchange pattern...

public interface Foo {
  void someInOnlyMethod(Document input);
  void anotherInOnlyMethod(String input);
  
  @MyAsyncService
  String someInOutMethod(String input); 
}

This provides a number of benefits...

• you can choose the right middleware solution for your deployment and switch at any time
• you don't have to spend a large amount of time learning the specifics of any particular technology, whether its JMS or JavaSpace or Hibernate or JPA or iBatis whatever

For example if you want to implement some kind of message passing, remoting, reliable load balancing or asynchronous processing in your application we recommend you use Camel annotations to bind your services and business logic to Camel Components which means you can then easily switch between things like

• in JVM messaging with SEDA
• using JMS via ActiveMQ or other JMS providers for reliable load balancing, grid or publish and subscribe
• for low volume, but easier administration since you're probably already using a database you could use
  • Hibernate or JPA to use an entity bean / table as a queue
  • iBatis to work with SQL
  • JDBC for raw SQL access
• use JavaSpace

How to decouple from middleware APIs

The best approach when using remoting is to use Spring Remoting which can then use any messaging or remoting technology under the covers. When using Camel's implementation you can then use any of the Camel Components along with any of the Enterprise Integration Patterns.

Another approach is to bind Java beans to Camel endpoints via the Bean Integration. For example using POJO Consuming and POJO Producing you can avoid using any Camel APIs to decouple your code both from middleware APIs and Camel APIs!

Visualisation

Camel supports the visualisation of your Enterprise Integration Patterns using the GraphViz DOT files which can either be rendered directly via a suitable GraphViz tool or turned into HTML, PNG or SVG files via the Camel Maven Plugin.

Here is a typical example of the kind of thing we can generate

If you click on the actual generated htmlyou will see that you can navigate from an EIP node to its pattern page, along with getting hover-over tool tips ec.

How to generate

See Camel Dot Maven Goal or the other maven goals Camel Maven Plugin

For OS X users

If you are using OS X then you can open the DOT file using graphviz which will then automatically re-render if it changes, so you end up with a real time graphical representation of the topic and queue hierarchies!

Also if you want to edit the layout a little before adding it to a wiki to distribute to your team, open the DOT file with OmniGraffle then just edit away

Business Activity Monitoring

The Camel BAM module provides a Business Activity Monitoring (BAM) framework for testing business processes across multiple message exchanges on different Endpoint instances.

Consider, for example, a simple system in which you submit Purchase Orders into system A and then receive Invoices from system B. You might want to test that, for a given Purchase Order, you receive a matching Invoice from system B within a specific time period.

How Camel BAM Works

Camel BAM uses a Correlation Identifier on an input message to determine the Process Instance to which it belongs. The process instance is an entity bean which can maintain state for each Activity (where an activity typically maps to a single endpoint - such as the submission of Purchase Orders or the receipt of Invoices).

You can then add rules to be triggered when a message is received on any activity - such as to set time expectations or perform real time reconciliation of values across activities.

Simple Example

The following example shows how to perform some time based rules on a simple business process of 2 activities - A and B - which correspond with Purchase Orders and Invoices in the example above. If you would like to experiment with this scenario, you may edit this Test Case, which defines the activities and rules, and then tests that they work.

As you can see in the above example, we first define two activities, and then rules to specify when we expect them to complete for a process instance and when an error condition should be raised.p. The ProcessBuilder is a RouteBuilder and can be added to any CamelContext.

Complete Example

For a complete example please see the BAM Example, which is part of the standard Camel Examples

Use Cases

In the world of finance, a common requirement is tracking trades. Often a trader will submit a Front Office Trade which then flows through the Middle Office and Back Office through various systems to settle the trade so that money is exchanged. You may wish to test that the front and back office trades match up within a certain time period; if they don't match or a back office trade does not arrive within a required amount of time, you might signal an alarm.

Extract Transform Load (ETL)

The ETL (Extract, Transform, Load) is a mechanism for loading data into systems or databases using some kind of Data Format from a variety of sources; often files then using Pipes and Filters, Message Translator and possible other Enterprise Integration Patterns.

So you could query data from various Camel Components such as File, HTTP or JPA, perform multiple patterns such as Splitter or Message Translator then send the messages to some other Component.

To show how this all fits together, try the ETL Example

Mock Component

Testing Summary Include

The Mock component provides a powerful declarative testing mechanism, which is similar to jMock in that it allows declarative expectations to be created on any Mock endpoint before a test begins. Then the test is run, which typically fires messages to one or more endpoints, and finally the expectations can be asserted in a test case to ensure the system worked as expected.

This allows you to test various things like:

• The correct number of messages are received on each endpoint,
• The correct payloads are received, in the right order,
• Messages arrive on an endpoint in order, using some Expression to create an order testing function,
• Messages arrive match some kind of Predicate such as that specific headers have certain values, or that parts of the messages match some predicate, such as by evaluating an XPath or XQuery Expression.

Note that there is also the Test endpoint which is a Mock endpoint, but which uses a second endpoint to provide the list of expected message bodies and automatically sets up the Mock endpoint assertions. In other words, it's a Mock endpoint that automatically sets up its assertions from some sample messages in a File or database, for example.

URI format

Where someName can be any string that uniquely identifies the endpoint.

You can append query options to the URI in the following format, ?option=value&option=value&...

Options

Simple Example

Here's a simple example of Mock endpoint in use. First, the endpoint is resolved on the context. Then we set an expectation, and then, after the test has run, we assert that our expectations have been met.

You typically always call the assertIsSatisfied() method to test that the expectations were met after running a test.

Camel will by default wait 10 seconds when the assertIsSatisfied() is invoked. This can be configured by setting the setResultWaitTime(millis) method.

Using assertPeriod

Available as of Camel 2.7
When the assertion is satisfied then Camel will stop waiting and continue from the assertIsSatisfied method. That means if a new message arrives on the mock endpoint, just a bit later, that arrival will not affect the outcome of the assertion. Suppose you do want to test that no new messages arrives after a period thereafter, then you can do that by setting the setAssertPeriod method, for example:

Setting expectations

You can see from the javadoc of MockEndpoint the various helper methods you can use to set expectations. The main methods are as follows:

Here's another example:

Adding expectations to specific messages

In addition, you can use the message(int messageIndex) method to add assertions about a specific message that is received.

For example, to add expectations of the headers or body of the first message (using zero-based indexing like java.util.List), you can use the following code:

There are some examples of the Mock endpoint in use in the camel-core processor tests.

Mocking existing endpoints

Available as of Camel 2.7

Camel now allows you to automatically mock existing endpoints in your Camel routes.

Suppose you have the given route below:

You can then use the adviceWith feature in Camel to mock all the endpoints in a given route from your unit test, as shown below:

Notice that the mock endpoints is given the uri mock:<endpoint>, for example mock:direct:foo. Camel logs at INFO level the endpoints being mocked:

Its also possible to only mock certain endpoints using a pattern. For example to mock all log endpoints you do as shown:

The pattern supported can be a wildcard or a regular expression. See more details about this at Intercept as its the same matching function used by Camel.

Mocking existing endpoints using the camel-test component

Instead of using the adviceWith to instruct Camel to mock endpoints, you can easily enable this behavior when using the camel-test Test Kit.
The same route can be tested as follows. Notice that we return "*" from the isMockEndpoints method, which tells Camel to mock all endpoints.
If you only want to mock all log endpoints you can return "log*" instead.

Mocking existing endpoints with XML DSL

If you do not use the camel-test component for unit testing (as shown above) you can use a different approach when using XML files for routes.
The solution is to create a new XML file used by the unit test and then include the intended XML file which has the route you want to test.

Suppose we have the route in the camel-route.xml file:

Then we create a new XML file as follows, where we include the camel-route.xml file and define a spring bean with the class org.apache.camel.impl.InterceptSendToMockEndpointStrategy which tells Camel to mock all endpoints:

Then in your unit test you load the new XML file (test-camel-route.xml) instead of camel-route.xml.

To only mock all Log endpoints you can define the pattern in the constructor for the bean:

Mocking endpoints and skip sending to original endpoint

Available as of Camel 2.10

Sometimes you want to easily mock and skip sending to a certain endpoints. So the message is detoured and send to the mock endpoint only. From Camel 2.10 onwards you can now use the mockEndpointsAndSkip method using AdviceWith or the Test Kit. The example below will skip sending to the two endpoints "direct:foo", and "direct:bar".

The same example using the Test Kit

Limiting the number of messages to keep

Available as of Camel 2.10

The Mock endpoints will by default keep a copy of every Exchange that it received. So if you test with a lot of messages, then it will consume memory.
From Camel 2.10 onwards we have introduced two options retainFirst and retainLast that can be used to specify to only keep N'th of the first and/or last Exchanges.

For example in the code below, we only want to retain a copy of the first 5 and last 5 Exchanges the mock receives.

Using this has some limitations. The getExchanges() and getReceivedExchanges() methods on the MockEndpoint will return only the retained copies of the Exchanges. So in the example above, the list will contain 10 Exchanges; the first five, and the last five.
The retainFirst and retainLast options also have limitations on which expectation methods you can use. For example the expectedXXX methods that work on message bodies, headers, etc. will only operate on the retained messages. In the example above they can test only the expectations on the 10 retained messages.

Testing with arrival times

Available as of Camel 2.7

The Mock endpoint stores the arrival time of the message as a property on the Exchange.

You can use this information to know when the message arrived on the mock. But it also provides foundation to know the time interval between the previous and next message arrived on the mock. You can use this to set expectations using the arrives DSL on the Mock endpoint.

For example to say that the first message should arrive between 0-2 seconds before the next you can do:

You can also define this as that 2nd message (0 index based) should arrive no later than 0-2 seconds after the previous:

You can also use between to set a lower bound. For example suppose that it should be between 1-4 seconds:

You can also set the expectation on all messages, for example to say that the gap between them should be at most 1 second:

Endpoint See Also

• Spring Testing
• Testing

Testing

Testing is a crucial activity in any piece of software development or integration. Typically Camel Riders use various different technologies wired together in a variety of patterns with different expression languages together with different forms of Bean Integration and Dependency Injection so its very easy for things to go wrong! . Testing is the crucial weapon to ensure that things work as you would expect.

Camel is a Java library so you can easily wire up tests in whatever unit testing framework you use (JUnit 3.x (deprecated), 4.x, or TestNG). However the Camel project has tried to make the testing of Camel as easy and powerful as possible so we have introduced the following features.

Testing Mechanisms

The following mechanisms are supported:

In all approaches the test classes look pretty much the same in that they all reuse the Camel binding and injection annotations.

Camel Test Example

Here is the Camel Test example:{snippet:lang=java|id=example|url=camel/trunk/components/camel-test/src/test/java/org/apache/camel/test/patterns/FilterTest.java}Notice how it derives from the Camel helper class CamelTestSupport but has no CDI, Spring or Guice dependency injection configuration but instead overrides the createRouteBuilder() method.

CDI Test Example

Here is the CDI Testing example:{snippet:lang=java|id=example|url=camel/trunk/components/camel-test-cdi/src/test/java/org/apache/camel/test/cdi/FilterTest.java}You can find more testing patterns illustrated in the camel-example-cdi-test example and the test classes that come with it.

Spring Test with XML Config Example

Here is the Spring Testing example using XML Config:{snippet:lang=java|id=example|url=camel/trunk/components/camel-spring/src/test/java/org/apache/camel/spring/patterns/FilterTest.java}Notice that we use @DirtiesContext on the test methods to force Spring Testing to automatically reload the CamelContext after each test method - this ensures that the tests don't clash with each other, e.g., one test method sending to an endpoint that is then reused in another test method.

Also note the use of @ContextConfiguration to indicate that by default we should look for the FilterTest-context.xml on the classpath to configure the test case which looks like this:{snippet:lang=xml|id=example|url=camel/trunk/components/camel-spring/src/test/resources/org/apache/camel/spring/patterns/FilterTest-context.xml}

Spring Test with Java Config Example

Here is the Spring Testing example using Java Config.

For more information see Spring Java Config.{snippet:lang=java|id=example|url=camel/trunk/components/camel-spring-javaconfig/src/test/java/org/apache/camel/spring/javaconfig/patterns/FilterTest.java}This is similar to the XML Config example above except that there is no XML file and instead the nested ContextConfig class does all of the configuration; so your entire test case is contained in a single Java class. We currently have to reference by class name this class in the @ContextConfiguration which is a bit ugly. Please vote for SJC-238 to address this and make Spring Test work more cleanly with Spring JavaConfig.

Its totally optional but for the ContextConfig implementation we derive from SingleRouteCamelConfiguration which is a helper Spring Java Config class which will configure the CamelContext for us and then register the RouteBuilder we create.

Since Camel 2.11.0 you can use the CamelSpringJUnit4ClassRunner with CamelSpringDelegatingTestContextLoader like example using Java Config with CamelSpringJUnit4ClassRunner:{snippet:lang=java|id=example|url=camel/trunk/components/camel-spring-javaconfig/src/test/java/org/apache/camel/spring/javaconfig/test/CamelSpringDelegatingTestContextLoaderTest.java}

Spring Test with XML Config and Declarative Configuration Example

Here is a Camel test support enhanced Spring Testing example using XML Config and pure Spring Test based configuration of the Camel Context:{snippet:lang=java|id=e1|url=camel/trunk/components/camel-test-spring/src/test/java/org/apache/camel/test/spring/CamelSpringJUnit4ClassRunnerPlainTest.java}Notice how a custom test runner is used with the @RunWith annotation to support the features of CamelTestSupport through annotations on the test class. See Spring Testing for a list of annotations you can use in your tests.

Blueprint Test

Here is the Blueprint Testing example using XML Config:{snippet:lang=java|id=example|url=camel/trunk/components/camel-test-blueprint/src/test/java/org/apache/camel/test/blueprint/DebugBlueprintTest.java}Also notice the use of getBlueprintDescriptors to indicate that by default we should look for the camelContext.xml in the package to configure the test case which looks like this:{snippet:lang=xml|id=example|url=camel/trunk/components/camel-test-blueprint/src/test/resources/org/apache/camel/test/blueprint/camelContext.xml}

Testing Endpoints

Camel provides a number of endpoints which can make testing easier.

The main endpoint is the Mock endpoint which allows expectations to be added to different endpoints; you can then run your tests and assert that your expectations are met at the end.

Stubbing out physical transport technologies

If you wish to test out a route but want to avoid actually using a real physical transport (for example to unit test a transformation route rather than performing a full integration test) then the following endpoints can be useful.

Testing existing routes

Camel provides some features to aid during testing of existing routes where you cannot or will not use Mock etc. For example you may have a production ready route which you want to test with some 3rd party API which sends messages into this route.

Camel Test

As a simple alternative to using CDI Testing, Spring Testing or Guice the camel-test module was introduced so you can perform powerful Testing of your Enterprise Integration Patterns easily.

Adding to your pom.xml

To get started using Camel Test you will need to add an entry to your pom.xml:

JUnit

TestNG

Available as of Camel 2.8

You might also want to add slf4j and log4j to ensure nice logging messages (and maybe adding a log4j.properties file into your src/test/resources directory).

Writing your test

You firstly need to derive from the class CamelTestSupport (org.apache.camel.test.CamelTestSupport, org.apache.camel.test.junit4.CamelTestSupport, or org.apache.camel.testng.CamelTestSupport for JUnit 3.x, JUnit 4.x, and TestNG, respectively) and typically you will need to override the createRouteBuilder() or createRouteBuilders() method to create routes to be tested.

Here is an example.{snippet:lang=java|id=example|url=camel/trunk/components/camel-test/src/test/java/org/apache/camel/test/patterns/FilterTest.java}Note: how you can use the various Camel binding and injection annotations to inject individual Endpoint objects - particularly the Mock endpoints which are very useful for Testing. Also you can inject producer objects such as ProducerTemplate or some application code interface for sending messages or invoking services.

Features Provided by CamelTestSupport

The various CamelTestSupport classes provide a standard set of behaviors relating to the CamelContext used to host the route(s) under test.  The classes provide a number of methods that allow a test to alter the configuration of the CamelContext used.  The following table describes the available customization methods and the default behavior of tests that are built from a CamelTestSupport class.

JNDI

Camel uses a Registry to allow you to configure Component or Endpoint instances or Beans used in your routes. If you are not using Spring or OSGi then JNDI is used as the default registry implementation.

So you will also need to create a jndi.properties file in your src/test/resources directory so that there is a default registry available to initialize the CamelContext.

Here is an example jndi.properties file

Dynamically Assigning Ports

Available as of Camel 2.7

Tests that use port numbers will fail if that port is already on use. AvailablePortFinder provides methods for finding unused port numbers at run time.

Setup CamelContext once per class, or per every test method

Available as of Camel 2.8

The Camel Test kit will by default setup and shutdown CamelContext per every test method in your test class. So for example if you have 3 test methods, then CamelContext is started and shutdown after each test, that is 3 times.

You may want to do this once, to share the CamelContext between test methods, to speedup unit testing. This requires the use of JUnit 4! In your unit test method you have to extend the org.apache.camel.test.junit4.CamelTestSupport or the org.apache.camel.test.junit4.CamelSpringTestSupport test class and override the isCreateCamelContextPerClass method and return true as shown in the following example:{snippet:id=example|lang=java|title=Setup CamelContext once per class|url=camel/trunk/components/camel-test/src/test/java/org/apache/camel/test/patterns/FilterCreateCamelContextPerClassTest.java}

See Also

• Testing
• Mock
• Test

Spring Testing

Testing is a crucial part of any development or integration work. The Spring Framework offers a number of features that makes it easy to test while using Spring for Inversion of Control which works with JUnit 3.x, JUnit 4.x, and TestNG.

We can use Spring for IoC and the Camel Mock and Test endpoints to create sophisticated integration/unit tests that are easy to run and debug inside your IDE.  There are three supported approaches for testing with Spring in Camel.

CamelSpringTestSupport

The following Spring test support classes:

• org.apache.camel.test.CamelSpringTestSupport
• org.apache.camel.test.junit4.CamelSpringTestSupport, and
• org.apache.camel.testng.CamelSpringTestSupport

extend their non-Spring aware counterparts:

• org.apache.camel.test.CamelTestSupport
• org.apache.camel.test.junit4.CamelTestSupport, and 
• org.apache.camel.testng.CamelTestSupport

and deliver integration with Spring into your test classes.  

Instead of instantiating the CamelContext and routes programmatically, these classes rely on a Spring context to wire the needed components together.  If your test extends one of these classes, you must provide the Spring context by implementing the following method.

You are responsible for the instantiation of the Spring context in the method implementation.  All of the features available in the non-Spring aware counterparts from Camel Test are available in your test.

Plain Spring Test

In this approach, your test classes directly inherit from the Spring Test abstract test classes or use the JUnit 4.x test runner provided in Spring Test.  This approach supports dependency injection into your test class and the full suite of Spring Test annotations. However, it does not support the features provided by the CamelSpringTestSupport classes.

Plain Spring Test using JUnit 3.x with XML Config Example

Here is a simple unit test using JUnit 3.x support from Spring Test using XML Config.{snippet:lang=java|id=example|url=camel/trunk/components/camel-spring/src/test/java/org/apache/camel/spring/patterns/FilterTest.java}Notice that we use @DirtiesContext on the test methods to force Spring Testing to automatically reload the CamelContext after each test method - this ensures that the tests don't clash with each other, e.g., one test method sending to an endpoint that is then reused in another test method.

Also notice the use of @ContextConfiguration to indicate that by default we should look for the file FilterTest-context.xml on the classpath to configure the test case. The test context looks like:{snippet:lang=xml|id=example|url=camel/trunk/components/camel-spring/src/test/resources/org/apache/camel/spring/patterns/FilterTest-context.xml}This test will load a Spring XML configuration file called FilterTest-context.xml from the classpath in the same package structure as the FilterTest class and initialize it along with any Camel routes we define inside it, then inject the CamelContext instance into our test case.

For instance, like this maven folder layout:

Plain Spring Test Using JUnit 4.x With Java Config Example

You can completely avoid using an XML configuration file by using Spring Java Config.  Here is a unit test using JUnit 4.x support from Spring Test using Java Config.{snippet:lang=java|id=example|url=camel/trunk/components/camel-spring-javaconfig/src/test/java/org/apache/camel/spring/javaconfig/patterns/FilterTest.java}This is similar to the XML Config example above except that there is no XML file and instead the nested ContextConfig class does all of the configuration; so your entire test case is contained in a single Java class. We currently have to reference by class name this class in the @ContextConfiguration which is a bit ugly. Please vote for SJC-238 to address this and make Spring Test work more cleanly with Spring JavaConfig.

Plain Spring Test Using JUnit 4.0.x Runner With XML Config

You can avoid extending Spring classes by using the SpringJUnit4ClassRunner provided by Spring Test.  This custom JUnit runner means you are free to choose your own class hierarchy while retaining all the capabilities of Spring Test.

Plain Spring Test Using JUnit 4.1.x Runner With XML Config

You can avoid extending Spring classes by using the SpringJUnit4ClassRunner provided by Spring Test.  This custom JUnit runner means you are free to choose your own class hierarchy while retaining all the capabilities of Spring Test.

Camel Enhanced Spring Test

Using the org.apache.camel.test.junit4.CamelSpringJUnit4ClassRunner runner with the @RunWith annotation or extending org.apache.camel.testng.AbstractCamelTestNGSpringContextTests provides the full feature set of Spring Test with support for the feature set provided in the CamelTestSupport classes.  

A number of Camel specific annotations have been developed in order to provide for declarative manipulation of the Camel context(s) involved in the test.  These annotations free your test classes from having to inherit from the CamelSpringTestSupport classes and also reduce the amount of code required to customize the tests.

The following example illustrates the use of the @MockEndpoints annotation in order to setup mock endpoints as interceptors on all endpoints using the Camel Log component and the @DisableJmx annotation to enable JMX which is disabled during tests by default.  

Adding More Mock Expectations

If you wish to programmatically add any new assertions to your test you can easily do so with the following. Notice how we use @EndpointInject to inject a Camel endpoint into our code then the Mock API to add an expectation on a specific message.

Further Processing the Received Messages

Sometimes once a Mock endpoint has received some messages you want to then process them further to add further assertions that your test case worked as you expect.

So you can then process the received message exchanges if you like...

Sending and Receiving Messages

It might be that the Enterprise Integration Patterns you have defined in either Spring XML or using the Java DSL do all of the sending and receiving and you might just work with the Mock endpoints as described above. However sometimes in a test case its useful to explicitly send or receive messages directly.

To send or receive messages you should use the Bean Integration mechanism. For example to send messages inject a ProducerTemplate using the @EndpointInject annotation then call the various send methods on this object to send a message to an endpoint. To consume messages use the @MessageDriven annotation on a method to have the method invoked when a message is received.

See Also

• A real example test case using Mock and Spring along with its Spring XML
• Bean Integration
• Mock endpoint
• Test endpoint

Camel Guice

We have support for Google Guice as a dependency injection framework.

Maven users will need to add the following dependency to their pom.xml for this component:

<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-guice</artifactId>
    <version>x.x.x</version>
    <!-- use the same version as your Camel core version -->
</dependency>

Dependency Injecting Camel with Guice

The GuiceCamelContext is designed to work nicely inside Guice. You then need to bind it using some Guice Module.

The camel-guice library comes with a number of reusable Guice Modules you can use if you wish - or you can bind the GuiceCamelContext yourself in your own module.

• CamelModule is the base module which binds the GuiceCamelContext but leaves it up you to bind the RouteBuilder instances
• CamelModuleWithRouteTypes extends CamelModule so that in the constructor of the module you specify the RouteBuilder classes or instances to use
• CamelModuleWithMatchingRoutes extends CamelModule so that all bound RouteBuilder instances will be injected into the CamelContext or you can supply an optional Matcher to find RouteBuilder instances matching some kind of predicate.

So you can specify the exact RouteBuilder instances you want

Injector injector = Guice.createInjector(new CamelModuleWithRouteTypes(MyRouteBuilder.class, AnotherRouteBuilder.class));
// if required you can lookup the CamelContext
CamelContext camelContext = injector.getInstance(CamelContext.class);

Or inject them all

Injector injector = Guice.createInjector(new CamelModuleWithRouteTypes());
// if required you can lookup the CamelContext
CamelContext camelContext = injector.getInstance(CamelContext.class);

You can then use Guice in the usual way to inject the route instances or any other dependent objects.

Bootstrapping with JNDI

A common pattern used in J2EE is to bootstrap your application or root objects by looking them up in JNDI. This has long been the approach when working with JMS for example - looking up the JMS ConnectionFactory in JNDI for example.

You can follow a similar pattern with Guice using the GuiceyFruit JNDI Provider which lets you bootstrap Guice from a jndi.properties file which can include the Guice Modules to create along with environment specific properties you can inject into your modules and objects.

If the jndi.properties is conflict with other component, you can specify the jndi properties file name in the Guice Main with option -j or -jndiProperties with the properties file location to let Guice Main to load right jndi properties file.

Configuring Component, Endpoint or RouteBuilder instances

You can use Guice to dependency inject whatever objects you need to create, be it an Endpoint, Component, RouteBuilder or arbitrary bean used within a route.

The easiest way to do this is to create your own Guice Module class which extends one of the above module classes and add a provider method for each object you wish to create. A provider method is annotated with @Provides as follows

public class MyModule extends CamelModuleWithMatchingRoutes {

    @Provides
    @JndiBind("jms")
    JmsComponent jms(@Named("activemq.brokerURL") String brokerUrl) {
        return JmsComponent.jmsComponent(new ActiveMQConnectionFactory(brokerUrl));
    }
}

You can optionally annotate the method with @JndiBind to bind the object to JNDI at some name if the object is a component, endpoint or bean you wish to refer to by name in your routes.

You can inject any environment specific properties (such as URLs, machine names, usernames/passwords and so forth) from the jndi.properties file easily using the @Named annotation as shown above. This allows most of your configuration to be in Java code which is typesafe and easily refactorable - then leaving some properties to be environment specific (the jndi.properties file) which you can then change based on development, testing, production etc.

Creating multiple RouteBuilder instances per type

It is sometimes useful to create multiple instances of a particular RouteBuilder with different configurations.

To do this just create multiple provider methods for each configuration; or create a single provider method that returns a collection of RouteBuilder instances.

For example

import org.apache.camel.guice.CamelModuleWithMatchingRoutes;
import com.google.common.collect.Lists;

public class MyModule extends CamelModuleWithMatchingRoutes {

    @Provides
    @JndiBind("foo")
    Collection<RouteBuilder> foo(@Named("fooUrl") String fooUrl) {
        return Lists.newArrayList(new MyRouteBuilder(fooUrl), new MyRouteBuilder("activemq:CheeseQueue"));
    }
}

See Also

• there are a number of Examples you can look at to see Guice and Camel being used such as Guice JMS Example
• Guice Maven Plugin for running your Guice based routes via Maven

Templating

When you are testing distributed systems its a very common requirement to have to stub out certain external systems with some stub so that you can test other parts of the system until a specific system is available or written etc.

A great way to do this is using some kind of Template system to generate responses to requests generating a dynamic message using a mostly-static body.

There are a number of templating components included in the Camel distribution you could use

• FreeMarker
• Mustache
• StringTemplate
• Velocity
• XQuery
• XSLT

or the following external Camel components

• Scalate

Example

Here's a simple example showing how we can respond to InOut requests on the My.Queue queue on ActiveMQ with a template generated response. The reply would be sent back to the JMSReplyTo Destination.

from("activemq:My.Queue").
  to("velocity:com/acme/MyResponse.vm");

If you want to use InOnly and consume the message and send it to another destination you could use

from("activemq:My.Queue").
  to("velocity:com/acme/MyResponse.vm").
  to("activemq:Another.Queue");

See Also

• Mock for details of mock endpoint testing (as opposed to template based stubs).

Database

Camel can work with databases in a number of different ways. This document tries to outline the most common approaches.

Database endpoints

Camel provides a number of different endpoints for working with databases

• JPA for working with hibernate, openjpa or toplink. When consuming from the endpoints entity beans are read (and deleted/updated to mark as processed) then when producing to the endpoints they are written to the database (via insert/update).
• iBATIS similar to the above but using Apache iBATIS
• JDBC similar though using explicit SQL
• SQL uses spring-jdbc behind the scene for the actual SQL handling. The difference between this component and JDBC component is that in case of SQL the query is a property of the endpoint and it uses message payload as parameters passed to the query

Database pattern implementations

Various patterns can work with databases as follows

• Idempotent Consumer
• Aggregator
• BAM for business activity monitoring

Parallel Processing and Ordering

It is a common requirement to want to use parallel processing of messages for throughput and load balancing, while at the same time process certain kinds of messages in order.

How to achieve parallel processing

You can send messages to a number of Camel Components to achieve parallel processing and load balancing such as

• SEDA for in-JVM load balancing across a thread pool
• ActiveMQ or JMS for distributed load balancing and parallel processing
• JPA for using the database as a poor mans message broker

When processing messages concurrently, you should consider ordering and concurrency issues. These are described below

Concurrency issues

Note that there is no concurrency or locking issue when using ActiveMQ, JMS or SEDA by design; they are designed for highly concurrent use. However there are possible concurrency issues in the Processor of the messages i.e. what the processor does with the message?

For example if a processor of a message transfers money from one account to another account; you probably want to use a database with pessimistic locking to ensure that operation takes place atomically.

Ordering issues

As soon as you send multiple messages to different threads or processes you will end up with an unknown ordering across the entire message stream as each thread is going to process messages concurrently.

For many use cases the order of messages is not too important. However for some applications this can be crucial. e.g. if a customer submits a purchase order version 1, then amends it and sends version 2; you don't want to process the first version last (so that you loose the update). Your Processor might be clever enough to ignore old messages. If not you need to preserve order.

Recommendations

This topic is large and diverse with lots of different requirements; but from a high level here are our recommendations on parallel processing, ordering and concurrency

• for distributed locking, use a database by default, they are very good at it
• to preserve ordering across a JMS queue consider using Exclusive Consumers in the ActiveMQ component
• even better are Message Groups which allows you to preserve ordering across messages while still offering parallelisation via the JMSXGroupID header to determine what can be parallelized
• if you receive messages out of order you could use the Resequencer to put them back together again

A good rule of thumb to help reduce ordering problems is to make sure each single can be processed as an atomic unit in parallel (either without concurrency issues or using say, database locking); or if it can't, use a Message Group to relate the messages together which need to be processed in order by a single thread.

Using Message Groups with Camel

To use a Message Group with Camel you just need to add a header to the output JMS message based on some kind of Correlation Identifier to correlate messages which should be processed in order by a single thread - so that things which don't correlate together can be processed concurrently.

For example the following code shows how to create a message group using an XPath expression taking an invoice's product code as the Correlation Identifier

from("activemq:a").setHeader(JmsConstants.JMS_X_GROUP_ID, xpath("/invoice/productCode")).to("activemq:b");

You can of course use the Xml Configuration if you prefer

Asynchronous Processing

Overview

Camel supports a more complex asynchronous processing model. The asynchronous processors implement the org.apache.camel.AsyncProcessor interface which is derived from the more synchronous org.apache.camel.Processor interface. There are advantages and disadvantages when using asynchronous processing when compared to using the standard synchronous processing model.

Advantages:

• Processing routes that are composed fully of asynchronous processors do not use up threads waiting for processors to complete on blocking calls. This can increase the scalability of your system by reducing the number of threads needed to process the same workload.
• Processing routes can be broken up into SEDA processing stages where different thread pools can process the different stages. This means that your routes can be processed concurrently.

Disadvantages:

• Implementing asynchronous processors is more complex than implementing the synchronous versions.

When to Use

We recommend that processors and components be implemented the more simple synchronous APIs unless you identify a performance of scalability requirement that dictates otherwise. A Processor whose process() method blocks for a long time would be good candidates for being converted into an asynchronous processor.

Interface Details

public interface AsyncProcessor extends Processor {
   boolean process(Exchange exchange, AsyncCallback callback);
}

The AsyncProcessor defines a single process() method which is very similar to it's synchronous Processor.process() brethren.

Here are the differences:

• A non-null AsyncCallback MUST be supplied which will be notified when the exchange processing is completed.
• It MUST not throw any exceptions that occurred while processing the exchange. Any such exceptions must be stored on the exchange's Exception property.
• It MUST know if it will complete the processing synchronously or asynchronously. The method will return true if it does complete synchronously, otherwise it returns false.
• When the processor has completed processing the exchange, it must call the callback.done(boolean sync) method.
• The sync parameter MUST match the value returned by the process() method.

Implementing Processors that Use the AsyncProcessor API

All processors, even synchronous processors that do not implement the AsyncProcessor interface, can be coerced to implement the AsyncProcessor interface. This is usually done when you are implementing a Camel component consumer that supports asynchronous completion of the exchanges that it is pushing through the Camel routes. Consumers are provided a Processor object when created. All Processor object can be coerced to a AsyncProcessor using the following API:

Processor processor = ...
AsyncProcessor asyncProcessor = AsyncProcessorTypeConverter.convert(processor);

For a route to be fully asynchronous and reap the benefits to lower Thread usage, it must start with the consumer implementation making use of the asynchronous processing API. If it called the synchronous process() method instead, the consumer's thread would be forced to be blocked and in use for the duration that it takes to process the exchange.

It is important to take note that just because you call the asynchronous API, it does not mean that the processing will take place asynchronously. It only allows the possibility that it can be done without tying up the caller's thread. If the processing happens asynchronously is dependent on the configuration of the Camel route.

Normally, the the process call is passed in an inline inner AsyncCallback class instance which can reference the exchange object that was declared final. This allows it to finish up any post processing that is needed when the called processor is done processing the exchange.

Example.

final Exchange exchange = ...
AsyncProcessor asyncProcessor = ...
asyncProcessor.process(exchange, new AsyncCallback() {
    public void done(boolean sync) {

        if (exchange.isFailed()) {
            ... // do failure processing.. perhaps rollback etc.
        } else {
            ... // processing completed successfully, finish up 
                // perhaps commit etc.
        }
    }
});

Asynchronous Route Sequence Scenarios

Now that we have understood the interface contract of the AsyncProcessor, and have seen how to make use of it when calling processors, let's looks a what the thread model/sequence scenarios will look like for some sample routes.

The Jetty component's consumers support asynchronous processing through the use of continuations. Suffice to say it can take a HTTP request and pass it to a Camel route for asynchronous processing. If the processing is indeed asynchronous, it uses a Jetty continuation so that the HTTP request is 'parked' and the thread is released. Once the Camel route finishes processing the request, the Jetty component uses the AsyncCallback to tell Jetty to 'un-park' the request. Jetty un-parks the request, the HTTP response returned using the result of the exchange processing.

Notice that the jetty continuations feature is only used "If the processing is indeed async". This is why AsyncProcessor.process() implementations must accurately report if request is completed synchronously or not.

The jhc component's producer allows you to make HTTP requests and implement the AsyncProcessor interface. A route that uses both the jetty asynchronous consumer and the jhc asynchronous producer will be a fully asynchronous route and has some nice attributes that can be seen if we take a look at a sequence diagram of the processing route.

For the route:

from("jetty:http://localhost:8080/service")
    .to("jhc:http://localhost/service-impl");

The sequence diagram would look something like this:

The diagram simplifies things by making it looks like processors implement the AsyncCallback interface when in reality the AsyncCallback interfaces are inline inner classes, but it illustrates the processing flow and shows how two separate threads are used to complete the processing of the original HTTP request. The first thread is synchronous up until processing hits the jhc producer which issues the HTTP request. It then reports that the exchange processing will complete asynchronously using NIO to get the response back. Once the jhc component has received a full response it uses AsyncCallback.done() method to notify the caller. These callback notifications continue up until it reaches the original Jetty consumer which then un-parks the HTTP request and completes it by providing the response.

Mixing Synchronous and Asynchronous Processors

It is totally possible and reasonable to mix the use of synchronous and asynchronous processors/components. The pipeline processor is the backbone of a Camel processing route. It glues all the processing steps together. It is implemented as an AsyncProcessor and supports interleaving synchronous and asynchronous processors as the processing steps in the pipeline.

Let's say we have two custom asynchronous processors, namely: MyValidator and MyTransformation. Let's say we want to load file from the data/in directory validate them with the MyValidator() processor, transform them into JPA Java objects using MyTransformation and then insert them into the database using the JPA component. Let's say that the transformation process takes quite a bit of time and we want to allocate 20 threads to do parallel transformations of the input files. The solution is to make use of the thread processor. The thread is AsyncProcessor that forces subsequent processing in asynchronous thread from a thread pool.

The route might look like:

from("file:data/in")
  .process(new MyValidator())
  .threads(20)
  .process(new MyTransformation())
  .to("jpa:PurchaseOrder");

The sequence diagram would look something like this:

You would actually have multiple threads executing the second part of the thread sequence.

Staying Synchronous in an AsyncProcessor

Generally speaking you get better throughput processing when you process things synchronously. This is due to the fact that starting up an asynchronous thread and doing a context switch to it adds a little bit of of overhead. So it is generally encouraged that AsyncProcessor's do as much work as they can synchronously. When they get to a step that would block for a long time, at that point they should return from the process call and let the caller know that it will be completing the call asynchronously.

Implementing Virtual Topics on other JMS providers

ActiveMQ supports Virtual Topics since durable topic subscriptions kinda suck (see this page for more detail) mostly since they don't support Competing Consumers.

Most folks want Queue semantics when consuming messages; so that you can support Competing Consumers for load balancing along with things like Message Groups and Exclusive Consumers to preserve ordering or partition the queue across consumers.

However if you are using another JMS provider you can implement Virtual Topics by switching to ActiveMQ or you can use the following Camel pattern.

First here's the ActiveMQ approach.

• send to activemq:topic:VirtualTopic.Orders
• for consumer A consume from activemq:Consumer.A.VirtualTopic.Orders

When using another message broker use the following pattern

• send to jms:Orders
• add this route with a to() for each logical durable topic subscriber

  from("jms:Orders").to("jms:Consumer.A", "jms:Consumer.B", ...); 

• for consumer A consume from jms:Consumer.A

What's the Camel Transport for CXF

In CXF you offer or consume a webservice by defining its address. The first part of the address specifies the protocol to use. For example address="http://localhost:9000" in an endpoint configuration means your service will be offered using the http protocol on port 9000 of localhost. When you integrate Camel Tranport into CXF you get a new transport "camel". So you can specify address="camel://direct:MyEndpointName" to bind the CXF service address to a camel direct endpoint.

Technically speaking Camel transport for CXF is a component which implements the CXF transport API with the Camel core library. This allows you to easily use Camel's routing engine and integration patterns support together with your CXF services.

Integrate Camel into CXF transport layer

To include the Camel Tranport into your CXF bus you use the CamelTransportFactory. You can do this in Java as well as in Spring.

Setting up the Camel Transport in Spring

You can use the following snippet in your applicationcontext if you want to configure anything special. If you only want to activate the camel transport you do not have to do anything in your application context. As soon as you include the camel-cxf-transport jar (or camel-cxf.jar if your camel version is less than 2.7.x) in your app, cxf will scan the jar and load a CamelTransportFactory for you.

Integrating the Camel Transport in a programmatic way

Camel transport provides a setContext method that you could use to set the Camel context into the transport factory. If you want this factory take effect, you need to register the factory into the CXF bus. Here is a full example for you.

Configure the destination and conduit with Spring

Namespace

The elements used to configure an Camel transport endpoint are defined in the namespace http://cxf.apache.org/transports/camel. It is commonly referred to using the prefix camel. In order to use the Camel transport configuration elements, you will need to add the lines shown below to the beans element of your endpoint's configuration file. In addition, you will need to add the configuration elements' namespace to the xsi:schemaLocation attribute.

The destination element

You configure an Camel transport server endpoint using the camel:destination element and its children. The camel:destination element takes a single attribute, name, that specifies the WSDL port element that corresponds to the endpoint. The value for the name attribute takes the form portQName.camel-destination. The example below shows the camel:destination element that would be used to add configuration for an endpoint that was specified by the WSDL fragment <port binding="widgetSOAPBinding" name="widgetSOAPPort"> if the endpoint's target namespace was http://widgets.widgetvendor.net.

The camel:destination element for Spring has a number of child elements that specify configuration information. They are described below.

The conduit element

You configure a Camel transport client using the camel:conduit element and its children. The camel:conduit element takes a single attribute, name, that specifies the WSDL port element that corresponds to the endpoint. The value for the name attribute takes the form portQName.camel-conduit. For example, the code below shows the camel:conduit element that would be used to add configuration for an endpoint that was specified by the WSDL fragment <port binding="widgetSOAPBinding" name="widgetSOAPPort"> if the endpoint's target namespace was http://widgets.widgetvendor.net.

The camel:conduit element has a number of child elements that specify configuration information. They are described below.

Configure the destination and conduit with Blueprint

From Camel 2.11.x, Camel Transport supports to be configured with Blueprint.

If you are using blueprint, you should use the the namespace http://cxf.apache.org/transports/camel/blueprint and import the schema like the blow.

In blueprint camel:conduit camel:destination only has one camelContextId attribute, they doesn't support to specify the camel context in the camel destination.

Example Using Camel as a load balancer for CXF

This example shows how to use the camel load balancing feature in CXF. You need to load the configuration file in CXF and publish the endpoints on the address "camel://direct:EndpointA" and "camel://direct:EndpointB"

Complete Howto and Example for attaching Camel to CXF

Better JMS Transport for CXF Webservice using Apache Camel 

Introduction

When sending an Exchange to an Endpoint you can either use a Route or a ProducerTemplate. This works fine in many scenarios. However you may need to guarantee that an exchange is delivered to the same endpoint that you delivered a previous exchange on. For example in the case of delivering a batch of exchanges to a MINA socket you may need to ensure that they are all delivered through the same socket connection. Furthermore once the batch of exchanges have been delivered the protocol requirements may be such that you are responsible for closing the socket.

Using a Producer

To achieve fine grained control over sending exchanges you will need to program directly to a Producer. Your code will look similar to:

  CamelContext camelContext = ...

  // Obtain an endpoint and create the producer we will be using.
  Endpoint endpoint = camelContext.getEndpoint("someuri:etc");
  Producer producer = endpoint.createProducer();
  producer.start();

  try {
    // For each message to send...
    Object requestMessage = ...
    Exchange exchangeToSend = producer.createExchange();
    exchangeToSend().setBody(requestMessage);
    producer.process(exchangeToSend);
    ...

  } finally {
    // Tidy the producer up.
    producer.stop();
  }

In the case of using Apache MINA the producer.stop() invocation will cause the socket to be closed.

• OAuth Tutorial
  This tutorial demonstrates how to implement OAuth for a web application with Camel's gauth component. The sample application of this tutorial is also online at http://gauthcloud.appspot.com/

• Tutorial for Camel on Google App Engine
  This tutorial demonstrates the usage of the Camel Components for Google App Engine. The sample application of this tutorial is also online at http://camelcloud.appspot.com/

• Tutorial on Spring Remoting with JMS
  This tutorial is focused on different techniques with Camel for Client-Server communication.

• Report Incident - This tutorial introduces Camel steadily and is based on a real life integration problem
  This is a very long tutorial beginning from the start; its for entry level to Camel. Its based on a real life integration, showing how Camel can be introduced in an existing solution. We do this in baby steps. The tutorial is currently work in progress, so check it out from time to time. The tutorial explains some of the inner building blocks Camel uses under the covers. This is good knowledge to have when you start using Camel on a higher abstract level where it can do wonders in a few lines of routing DSL.

• Using Camel with ServiceMix a tutorial on using Camel inside Apache ServiceMix.

• Better JMS Transport for CXF Webservice using Apache Camel Describes how to use the Camel Transport for CXF to attach a CXF Webservice to a JMS Queue

• Tutorial how to use good old Axis 1.4 with Camel
  This tutorial shows that Camel does work with the good old frameworks such as AXIS that is/was widely used for WebService.

• Tutorial on using Camel in a Web Application
  This tutorial gives an overview of how to use Camel inside Tomcat, Jetty or any other servlet engine

• Tutorial on Camel 1.4 for Integration
  Another real-life scenario. The company sells widgets, with a somewhat unique business process (their customers periodically report what they've purchased in order to get billed). However every customer uses a different data format and protocol. This tutorial goes through the process of integrating (and testing!) several customers and their electronic reporting of the widgets they've bought, along with the company's response.

• Tutorial how to build a Service Oriented Architecture using Camel with OSGI - Updated 20/11/2009
  The tutorial has been designed in two parts. The first part introduces basic concept to create a simple SOA solution using Camel and OSGI and deploy it in a OSGI Server like Apache Felix Karaf and Spring DM Server while the second extends the ReportIncident tutorial part 4 to show How we can separate the different layers (domain, service, ...) of an application and deploy them in separate bundles. The Web Application has also be modified in order to communicate to the OSGI bundles.

• Several of the vendors on the Commercial Camel Offerings page also offer various tutorials, webinars, examples, etc.... that may be useful.

• Examples
  While not actual tutorials you might find working through the source of the various Examples useful.

Tutorial on Spring Remoting with JMS

Preface

This tutorial aims to guide the reader through the stages of creating a project which uses Camel to facilitate the routing of messages from a JMS queue to a Spring service. The route works in a synchronous fashion returning a response to the client.

Prerequisites

This tutorial uses Maven to setup the Camel project and for dependencies for artifacts.

Distribution

This sample is distributed with the Camel distribution as examples/camel-example-spring-jms.

About

This tutorial is a simple example that demonstrates more the fact how well Camel is seamless integrated with Spring to leverage the best of both worlds. This sample is client server solution using JMS messaging as the transport. The sample has two flavors of servers and also for clients demonstrating different techniques for easy communication.

The Server is a JMS message broker that routes incoming messages to a business service that does computations on the received message and returns a response.
The EIP patterns used in this sample are:

We use the following Camel components:

Create the Camel Project

Update the POM with Dependencies

First we need to have dependencies for the core Camel jars, spring, jms components, and finally ActiveMQ as the message broker.{snippet:id=e1|lang=xml|url=camel/trunk/examples/camel-example-spring-jms/pom.xml}As we use spring xml configuration for the ActiveMQ JMS broker we need this dependency:{snippet:id=e2|lang=xml|url=camel/trunk/examples/camel-example-spring-jms/pom.xml}

Writing the Server

Create the Spring Service

For this example the Spring service (our business service) on the server will be a simple multiplier which trebles in the received value.{snippet:id=e1|lang=java|url=camel/trunk/examples/camel-example-spring-jms/src/main/java/org/apache/camel/example/server/Multiplier.java}And the implementation of this service is:{snippet:id=e1|lang=java|url=camel/trunk/examples/camel-example-spring-jms/src/main/java/org/apache/camel/example/server/Treble.java}Notice that this class has been annotated with the @Service spring annotation. This ensures that this class is registered as a bean in the registry with the given name multiplier.

Define the Camel Routes

{snippet:id=e1|lang=java|url=camel/trunk/examples/camel-example-spring-jms/src/main/java/org/apache/camel/example/server/ServerRoutes.java}This defines a Camel route from the JMS queue named numbers to the Spring bean named multiplier. Camel will create a consumer to the JMS queue which forwards all received messages onto the the Spring bean, using the method named multiply.

Configure Spring

The Spring config file is placed under META-INF/spring as this is the default location used by the Camel Maven Plugin, which we will later use to run our server.
First we need to do the standard scheme declarations in the top. In the camel-server.xml we are using spring beans as the default bean: namespace and springs context:. For configuring ActiveMQ we use broker: and for Camel we of course have camel:. Notice that we don't use version numbers for the camel-spring schema. At runtime the schema is resolved in the Camel bundle. If we use a specific version number such as 1.4 then its IDE friendly as it would be able to import it and provide smart completion etc. See Xml Reference for further details.{snippet:id=e1|lang=xml|url=camel/trunk/examples/camel-example-spring-jms/src/main/resources/META-INF/spring/camel-server.xml}We use Spring annotations for doing IoC dependencies and its component-scan features comes to the rescue as it scans for spring annotations in the given package name:{snippet:id=e2|lang=xml|url=camel/trunk/examples/camel-example-spring-jms/src/main/resources/META-INF/spring/camel-server.xml}Camel will of course not be less than Spring in this regard so it supports a similar feature for scanning of Routes. This is configured as shown below.
Notice that we also have enabled the JMXAgent so we will be able to introspect the Camel Server with a JMX Console.{snippet:id=e3|lang=xml|url=camel/trunk/examples/camel-example-spring-jms/src/main/resources/META-INF/spring/camel-server.xml}The ActiveMQ JMS broker is also configured in this xml file. We set it up to listen on TCP port 61610.{snippet:id=e4|lang=xml|url=camel/trunk/examples/camel-example-spring-jms/src/main/resources/META-INF/spring/camel-server.xml}As this examples uses JMS then Camel needs a JMS component that is connected with the ActiveMQ broker. This is configured as shown below:{snippet:id=e5|lang=xml|url=camel/trunk/examples/camel-example-spring-jms/src/main/resources/META-INF/spring/camel-server.xml}Notice: The JMS component is configured in standard Spring beans, but the gem is that the bean id can be referenced from Camel routes - meaning we can do routing using the JMS Component by just using jms: prefix in the route URI. What happens is that Camel will find in the Spring Registry for a bean with the id="jms". Since the bean id can have arbitrary name you could have named it id="jmsbroker" and then referenced to it in the routing as from="jmsbroker:queue:numbers).to("multiplier");
We use the vm protocol to connect to the ActiveMQ server as its embedded in this application.

Run the Server

The Server is started using the org.apache.camel.spring.Main class that can start camel-spring application out-of-the-box. The Server can be started in several flavors:

• as a standard java main application - just start the org.apache.camel.spring.Main class
• using maven jave:exec
• using camel:run

In this sample as there are two servers (with and without AOP) we have prepared some profiles in maven to start the Server of your choice.
The server is started with:
mvn compile exec:java -PCamelServer

Writing The Clients

This sample has three clients demonstrating different Camel techniques for communication

• CamelClient using the ProducerTemplate for Spring template style coding
• CamelRemoting using Spring Remoting
• CamelEndpoint using the Message Endpoint EIP pattern using a neutral Camel API

Client Using The ProducerTemplate

We will initially create a client by directly using ProducerTemplate. We will later create a client which uses Spring remoting to hide the fact that messaging is being used.{snippet:id=e1|lang=xml|url=camel/trunk/examples/camel-example-spring-jms/src/main/resources/camel-client.xml}{snippet:id=e2|lang=xml|url=camel/trunk/examples/camel-example-spring-jms/src/main/resources/camel-client.xml}{snippet:id=e3|lang=xml|url=camel/trunk/examples/camel-example-spring-jms/src/main/resources/camel-client.xml}The client will not use the Camel Maven Plugin so the Spring XML has been placed in src/main/resources to not conflict with the server configs.

And the CamelClient source code:{snippet:id=e1|lang=java|url=camel/trunk/examples/camel-example-spring-jms/src/main/java/org/apache/camel/example/client/CamelClient.java}The ProducerTemplate is retrieved from a Spring ApplicationContext and used to manually place a message on the "numbers" JMS queue. The requestBody method will use the exchange pattern InOut, which states that the call should be synchronous, and that the caller expects a response.

Before running the client be sure that both the ActiveMQ broker and the CamelServer are running.

Client Using Spring Remoting

Spring Remoting "eases the development of remote-enabled services". It does this by allowing you to invoke remote services through your regular Java interface, masking that a remote service is being called.{snippet:id=e1|lang=xml|url=camel/trunk/examples/camel-example-spring-jms/src/main/resources/camel-client-remoting.xml}The snippet above only illustrates the different and how Camel easily can setup and use Spring Remoting in one line configurations.

The proxy will create a proxy service bean for you to use to make the remote invocations. The serviceInterface property details which Java interface is to be implemented by the proxy. The serviceUrl defines where messages sent to this proxy bean will be directed. Here we define the JMS endpoint with the "numbers" queue we used when working with Camel template directly. The value of the id property is the name that will be the given to the bean when it is exposed through the Spring ApplicationContext. We will use this name to retrieve the service in our client. I have named the bean multiplierProxy simply to highlight that it is not the same multiplier bean as is being used by CamelServer. They are in completely independent contexts and have no knowledge of each other. As you are trying to mask the fact that remoting is being used in a real application you would generally not include proxy in the name.

And the Java client source code:{snippet:id=e1|lang=java|url=camel/trunk/examples/camel-example-spring-jms/src/main/java/org/apache/camel/example/client/CamelClientRemoting.java}Again, the client is similar to the original client, but with some important differences.

1. The Spring context is created with the new camel-client-remoting.xml
2. We retrieve the proxy bean instead of a ProducerTemplate. In a non-trivial example you would have the bean injected as in the standard Spring manner.
3. The multiply method is then called directly. In the client we are now working to an interface. There is no mention of Camel or JMS inside our Java code.

Client Using Message Endpoint EIP Pattern

This client uses the Message Endpoint EIP pattern to hide the complexity to communicate to the Server. The Client uses the same simple API to get hold of the endpoint, create an exchange that holds the message, set the payload and create a producer that does the send and receive. All done using the same neutral Camel API for all the components in Camel. So if the communication was socket TCP based you just get hold of a different endpoint and all the java code stays the same. That is really powerful.

Okay enough talk, show me the code!{snippet:id=e1|lang=java|url=camel/trunk/examples/camel-example-spring-jms/src/main/java/org/apache/camel/example/client/CamelClientEndpoint.java}Switching to a different component is just a matter of using the correct endpoint. So if we had defined a TCP endpoint as: "mina:tcp://localhost:61610" then its just a matter of getting hold of this endpoint instead of the JMS and all the rest of the java code is exactly the same.

Run the Clients

The Clients is started using their main class respectively.

• as a standard java main application - just start their main class
• using maven jave:exec

In this sample we start the clients using maven:
mvn compile exec:java -PCamelClient
mvn compile exec:java -PCamelClientRemoting
mvn compile exec:java -PCamelClientEndpoint

Also see the Maven pom.xml file how the profiles for the clients is defined.

Using the Camel Maven Plugin

The Camel Maven Plugin allows you to run your Camel routes directly from Maven. This negates the need to create a host application, as we did with Camel server, simply to start up the container. This can be very useful during development to get Camel routes running quickly.

All that is required is a new plugin definition in your Maven POM. As we have already placed our Camel config in the default location (camel-server.xml has been placed in META-INF/spring/) we do not need to tell the plugin where the route definitions are located. Simply run mvn camel:run.

Using Camel JMX

Camel has extensive support for JMX and allows us to inspect the Camel Server at runtime. As we have enabled the JMXAgent in our tutorial we can fire up the jconsole and connect to the following service URI: service:jmx:rmi:///jndi/rmi://localhost:1099/jmxrmi/camel. Notice that Camel will log at INFO level the JMX Connector URI:

In the screenshot below we can see the route and its performance metrics:

See Also

• Spring Remoting with JMS Example on Amin Abbaspour's Weblog

Tutorial - camel-example-reportincident

Introduction

Creating this tutorial was inspired by a real life use-case I discussed over the phone with a colleague. He was working at a client whom uses a heavy-weight integration platform from a very large vendor. He was in talks with developer shops to implement a new integration on this platform. His trouble was the shop tripled the price when they realized the platform of choice. So I was wondering how we could do this integration with Camel. Can it be done, without tripling the cost .

This tutorial is written during the development of the integration. I have decided to start off with a sample that isn't Camel's but standard Java and then plugin Camel as we goes. Just as when people needed to learn Spring you could consume it piece by piece, the same goes with Camel.

The target reader is person whom hasn't experience or just started using Camel.

Motivation for this tutorial

I wrote this tutorial motivated as Camel lacked an example application that was based on the web application deployment model. The entire world hasn't moved to pure OSGi deployments yet.

The use-case

The goal is to allow staff to report incidents into a central administration. For that they use client software where they report the incident and submit it to the central administration. As this is an integration in a transition phase the administration should get these incidents by email whereas they are manually added to the database. The client software should gather the incident and submit the information to the integration platform that in term will transform the report into an email and send it to the central administrator for manual processing.

The figure below illustrates this process. The end users reports the incidents using the client applications. The incident is sent to the central integration platform as webservice. The integration platform will process the incident and send an OK acknowledgment back to the client. Then the integration will transform the message to an email and send it to the administration mail server. The users in the administration will receive the emails and take it from there.

In EIP patterns

We distill the use case as EIP patterns:

Parts

This tutorial is divided into sections and parts:

Section A: Existing Solution, how to slowly use Camel

Part 1 - This first part explain how to setup the project and get a webservice exposed using Apache CXF. In fact we don't touch Camel yet.

Part 2 - Now we are ready to introduce Camel piece by piece (without using Spring or any XML configuration file) and create the full feature integration. This part will introduce different Camel's concepts and How we can build our solution using them like :

• CamelContext
• Endpoint, Exchange & Producer
• Components : Log, File

Part 3 - Continued from part 2 where we implement that last part of the solution with the event driven consumer and how to send the email through the Mail component.

Section B: The Camel Solution

Part 4 - We now turn into the path of Camel where it excels - the routing.
Part 5 - Is about how embed Camel with Spring and using CXF endpoints directly in Camel
Part 6 - Showing a alternative solution primarily using XML instead of Java code

Links

• Introduction
• Part 1
• Part 2
• Part 3
• Part 4
• Part 5
• Part 6

Part 1

Prerequisites

This tutorial uses the following frameworks:

• Maven 3.0.4
• Apache Camel 2.10.0
• Apache CXF 2.6.1
• Spring 3.0.7

Note: The sample project can be downloaded, see the resources section.

Initial Project Setup

We want the integration to be a standard .war application that can be deployed in any web container such as Tomcat, Jetty or even heavy weight application servers such as WebLogic or WebSphere. There fore we start off with the standard Maven webapp project that is created with the following long archetype command:

mvn archetype:create -DgroupId=org.apache.camel -DartifactId=camel-example-reportincident -DarchetypeArtifactId=maven-archetype-webapp

Notice that the groupId etc. doens't have to be org.apache.camel it can be com.mycompany.whatever. But I have used these package names as the example is an official part of the Camel distribution.

Then we have the basic maven folder layout. We start out with the webservice part where we want to use Apache CXF for the webservice stuff. So we add this to the pom.xml

    <properties>
        <cxf-version>2.6.1</cxf-version>
    </properties>

    <dependency>
        <groupId>org.apache.cxf</groupId>
        <artifactId>cxf-rt-core</artifactId>
        <version>${cxf-version}</version>
    </dependency>
    <dependency>
        <groupId>org.apache.cxf</groupId>
        <artifactId>cxf-rt-frontend-jaxws</artifactId>
        <version>${cxf-version}</version>
    </dependency>
    <dependency>
        <groupId>org.apache.cxf</groupId>
        <artifactId>cxf-rt-transports-http</artifactId>
        <version>${cxf-version}</version>
    </dependency>

Developing the WebService

As we want to develop webservice with the contract first approach we create our .wsdl file. As this is a example we have simplified the model of the incident to only include 8 fields. In real life the model would be a bit more complex, but not to much.

We put the wsdl file in the folder src/main/webapp/WEB-INF/wsdl and name the file report_incident.wsdl.

<?xml version="1.0" encoding="ISO-8859-1"?>
<wsdl:definitions xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
	xmlns:tns="http://reportincident.example.camel.apache.org"
	xmlns:xs="http://www.w3.org/2001/XMLSchema"
	xmlns:http="http://schemas.xmlsoap.org/wsdl/http/"
	xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/"
	targetNamespace="http://reportincident.example.camel.apache.org">

	<!-- Type definitions for input- and output parameters for webservice -->
	<wsdl:types>
	<xs:schema targetNamespace="http://reportincident.example.camel.apache.org">
			<xs:element name="inputReportIncident">
				<xs:complexType>
					<xs:sequence>
						<xs:element type="xs:string"  name="incidentId"/>
						<xs:element type="xs:string"  name="incidentDate"/>
						<xs:element type="xs:string"  name="givenName"/>
						<xs:element type="xs:string"  name="familyName"/>
						<xs:element type="xs:string"  name="summary"/>
						<xs:element type="xs:string"  name="details"/>
						<xs:element type="xs:string"  name="email"/>
						<xs:element type="xs:string"  name="phone"/>
					</xs:sequence>
				</xs:complexType>
			</xs:element>
			<xs:element name="outputReportIncident">
				<xs:complexType>
					<xs:sequence>
						<xs:element type="xs:string" name="code"/>
					</xs:sequence>
				</xs:complexType>
			</xs:element>
		</xs:schema>
	</wsdl:types>

	<!-- Message definitions for input and output -->
	<wsdl:message name="inputReportIncident">
		<wsdl:part name="parameters" element="tns:inputReportIncident"/>
	</wsdl:message>
	<wsdl:message name="outputReportIncident">
		<wsdl:part name="parameters" element="tns:outputReportIncident"/>
	</wsdl:message>

	<!-- Port (interface) definitions -->
	<wsdl:portType name="ReportIncidentEndpoint">
		<wsdl:operation name="ReportIncident">
			<wsdl:input message="tns:inputReportIncident"/>
			<wsdl:output message="tns:outputReportIncident"/>
		</wsdl:operation>
	</wsdl:portType>

	<!-- Port bindings to transports and encoding - HTTP, document literal encoding is used -->
	<wsdl:binding name="ReportIncidentBinding" type="tns:ReportIncidentEndpoint">
		<soap:binding transport="http://schemas.xmlsoap.org/soap/http"/>
		<wsdl:operation name="ReportIncident">
			<soap:operation
				soapAction="http://reportincident.example.camel.apache.org/ReportIncident"
				style="document"/>
			<wsdl:input>
				<soap:body parts="parameters" use="literal"/>
			</wsdl:input>
			<wsdl:output>
				<soap:body parts="parameters" use="literal"/>
			</wsdl:output>
		</wsdl:operation>
	</wsdl:binding>

	<!-- Service definition -->
	<wsdl:service name="ReportIncidentService">
		<wsdl:port name="ReportIncidentPort" binding="tns:ReportIncidentBinding">
			<soap:address location="http://reportincident.example.camel.apache.org"/>
		</wsdl:port>
	</wsdl:service>

</wsdl:definitions>

CXF wsdl2java

Then we integration the CXF wsdl2java generator in the pom.xml so we have CXF generate the needed POJO classes for our webservice contract.
However at first we must configure maven to live in the modern world of Java 1.6 so we must add this to the pom.xml

			<!-- to compile with 1.6 -->
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-compiler-plugin</artifactId>
				<configuration>
					<source>1.6</source>
					<target>1.6</target>
				</configuration>
			</plugin>

And then we can add the CXF wsdl2java code generator that will hook into the compile goal so its automatic run all the time:

			<!-- CXF wsdl2java generator, will plugin to the compile goal -->
			<plugin>
				<groupId>org.apache.cxf</groupId>
				<artifactId>cxf-codegen-plugin</artifactId>
				<version>${cxf-version}</version>
				<executions>
					<execution>
						<id>generate-sources</id>
						<phase>generate-sources</phase>
						<configuration>
							<sourceRoot>${basedir}/target/generated/src/main/java</sourceRoot>
							<wsdlOptions>
								<wsdlOption>
									<wsdl>${basedir}/src/main/webapp/WEB-INF/wsdl/report_incident.wsdl</wsdl>
								</wsdlOption>
							</wsdlOptions>
						</configuration>
						<goals>
							<goal>wsdl2java</goal>
						</goals>
					</execution>
				</executions>
			</plugin>

You are now setup and should be able to compile the project. So running the mvn compile should run the CXF wsdl2java and generate the source code in the folder &{basedir}/target/generated/src/main/java that we specified in the pom.xml above. Since its in the target/generated/src/main/java maven will pick it up and include it in the build process.

Configuration of the web.xml

Next up is to configure the web.xml to be ready to use CXF so we can expose the webservice.
As Spring is the center of the universe, or at least is a very important framework in today's Java land we start with the listener that kick-starts Spring. This is the usual piece of code:

	<!-- the listener that kick-starts Spring -->
	<listener>
		<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
	</listener>

And then we have the CXF part where we define the CXF servlet and its URI mappings to which we have chosen that all our webservices should be in the path /webservices/

	<!-- CXF servlet -->
	<servlet>
		<servlet-name>CXFServlet</servlet-name>
		<servlet-class>org.apache.cxf.transport.servlet.CXFServlet</servlet-class>
		<load-on-startup>1</load-on-startup>
	</servlet>

	<!-- all our webservices are mapped under this URI pattern -->
	<servlet-mapping>
		<servlet-name>CXFServlet</servlet-name>
		<url-pattern>/webservices/*</url-pattern>
	</servlet-mapping>

Then the last piece of the puzzle is to configure CXF, this is done in a spring XML that we link to fron the web.xml by the standard Spring contextConfigLocation property in the web.xml

	<!-- location of spring xml files -->
	<context-param>
		<param-name>contextConfigLocation</param-name>
		<param-value>classpath:cxf-config.xml</param-value>
	</context-param>

We have named our CXF configuration file cxf-config.xml and its located in the root of the classpath. In Maven land that is we can have the cxf-config.xml file in the src/main/resources folder. We could also have the file located in the WEB-INF folder for instance <param-value>/WEB-INF/cxf-config.xml</param-value>.

Getting rid of the old jsp world

The maven archetype that created the basic folder structure also created a sample .jsp file index.jsp. This file src/main/webapp/index.jsp should be deleted.

Configuration of CXF

The cxf-config.xml is as follows:

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:jaxws="http://cxf.apache.org/jaxws"
       xsi:schemaLocation="
            http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
            http://cxf.apache.org/jaxws http://cxf.apache.org/schemas/jaxws.xsd">

    <import resource="classpath:META-INF/cxf/cxf.xml"/>
    <import resource="classpath:META-INF/cxf/cxf-extension-soap.xml"/>
    <import resource="classpath:META-INF/cxf/cxf-servlet.xml"/>

    <!-- implementation of the webservice -->
    <bean id="reportIncidentEndpoint" class="org.apache.camel.example.reportincident.ReportIncidentEndpointImpl"/>

    <!-- export the webservice using jaxws -->
    <jaxws:endpoint id="reportIncident"
                    implementor="#reportIncidentEndpoint"
                    address="/incident"
                    wsdlLocation="/WEB-INF/wsdl/report_incident.wsdl"
                    endpointName="s:ReportIncidentPort"
                    serviceName="s:ReportIncidentService"
                    xmlns:s="http://reportincident.example.camel.apache.org"/>

</beans>

The configuration is standard CXF and is documented at the Apache CXF website.

The 3 import elements is needed by CXF and they must be in the file.

Noticed that we have a spring bean reportIncidentEndpoint that is the implementation of the webservice endpoint we let CXF expose.
Its linked from the jaxws element with the implementator attribute as we use the # mark to identify its a reference to a spring bean. We could have stated the classname directly as implementor="org.apache.camel.example.reportincident.ReportIncidentEndpoint" but then we lose the ability to let the ReportIncidentEndpoint be configured by spring.
The address attribute defines the relative part of the URL of the exposed webservice. wsdlLocation is an optional parameter but for persons like me that likes contract-first we want to expose our own .wsdl contracts and not the auto generated by the frameworks, so with this attribute we can link to the real .wsdl file. The last stuff is needed by CXF as you could have several services so it needs to know which this one is. Configuring these is quite easy as all the information is in the wsdl already.

Implementing the ReportIncidentEndpoint

Phew after all these meta files its time for some java code so we should code the implementor of the webservice. So we fire up mvn compile to let CXF generate the POJO classes for our webservice and we are ready to fire up a Java editor.

You can use mvn idea:idea or mvn eclipse:eclipse to create project files for these editors so you can load the project. However IDEA has been smarter lately and can load a pom.xml directly.

As we want to quickly see our webservice we implement just a quick and dirty as it can get. At first beware that since its jaxws and Java 1.5 we get annotations for the money, but they reside on the interface so we can remove them from our implementations so its a nice plain POJO again:

package org.apache.camel.example.reportincident;

/**
 * The webservice we have implemented.
 */
public class ReportIncidentEndpointImpl implements ReportIncidentEndpoint {

    public OutputReportIncident reportIncident(InputReportIncident parameters) {
        System.out.println("Hello ReportIncidentEndpointImpl is called from " + parameters.getGivenName());

        OutputReportIncident out = new OutputReportIncident();
        out.setCode("OK");
        return out;
    }

}

We just output the person that invokes this webservice and returns a OK response. This class should be in the maven source root folder src/main/java under the package name org.apache.camel.example.reportincident. Beware that the maven archetype tool didn't create the src/main/java folder, so you should create it manually.

To test if we are home free we run mvn clean compile.

Running our webservice

Now that the code compiles we would like to run it inside a web container, for this purpose we make use of Jetty which we will bootstrap using it's plugin org.mortbay.jetty:maven-jetty-plugin:

       <build>
           <plugins>
               ...
               <!-- so we can run mvn jetty:run -->
               <plugin>
                   <groupId>org.mortbay.jetty</groupId>
                   <artifactId>maven-jetty-plugin</artifactId>
                   <version>${jetty-version}</version>
               </plugin>

Notice: We make use of the Jetty version being defined inside the Camel's Parent POM.

So to see if everything is in order we fire up jetty with mvn jetty:run and if everything is okay you should be able to access http://localhost:8080.
Jetty is smart that it will list the correct URI on the page to our web application, so just click on the link. This is smart as you don't have to remember the exact web context URI for your application - just fire up the default page and Jetty will help you.

So where is the damn webservice then? Well as we did configure the web.xml to instruct the CXF servlet to accept the pattern /webservices/* we should hit this URL to get the attention of CXF: http://localhost:8080/camel-example-reportincident/webservices.

 

Hitting the webservice

Now we have the webservice running in a standard .war application in a standard web container such as Jetty we would like to invoke the webservice and see if we get our code executed. Unfortunately this isn't the easiest task in the world - its not so easy as a REST URL, so we need tools for this. So we fire up our trusty webservice tool SoapUI and let it be the one to fire the webservice request and see the response.

Using SoapUI we sent a request to our webservice and we got the expected OK response and the console outputs the System.out so we are ready to code.

 

Remote Debugging

Okay a little sidestep but wouldn't it be cool to be able to debug your code when its fired up under Jetty? As Jetty is started from maven, we need to instruct maven to use debug mode.
Se we set the MAVEN_OPTS environment to start in debug mode and listen on port 5005.

MAVEN_OPTS=-Xmx512m -XX:MaxPermSize=128m -Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=5005

Then you need to restart Jetty so its stopped with ctrl + c. Remember to start a new shell to pickup the new environment settings. And start jetty again.

Then we can from our IDE attach a remote debugger and debug as we want.
First we configure IDEA to attach to a remote debugger on port 5005:

 

Then we set a breakpoint in our code ReportIncidentEndpoint and hit the SoapUI once again and we are breaked at the breakpoint where we can inspect the parameters:

 

Adding a unit test

Oh so much hard work just to hit a webservice, why can't we just use an unit test to invoke our webservice? Yes of course we can do this, and that's the next step.
First we create the folder structure src/test/java and src/test/resources. We then create the unit test in the src/test/java folder.

package org.apache.camel.example.reportincident;

import junit.framework.TestCase;

/**
 * Plain JUnit test of our webservice.
 */
public class ReportIncidentEndpointTest extends TestCase {

}

Here we have a plain old JUnit class. As we want to test webservices we need to start and expose our webservice in the unit test before we can test it. And JAXWS has pretty decent methods to help us here, the code is simple as:

    import javax.xml.ws.Endpoint;
    ...

    private static String ADDRESS = "http://localhost:9090/unittest";

    protected void startServer() throws Exception {
        // We need to start a server that exposes or webservice during the unit testing
        // We use jaxws to do this pretty simple
        ReportIncidentEndpointImpl server = new ReportIncidentEndpointImpl();
        Endpoint.publish(ADDRESS, server);
    }

The Endpoint class is the javax.xml.ws.Endpoint that under the covers looks for a provider and in our case its CXF - so its CXF that does the heavy lifting of exposing out webservice on the given URL address. Since our class ReportIncidentEndpointImpl implements the interface ReportIncidentEndpoint that is decorated with all the jaxws annotations it got all the information it need to expose the webservice. Below is the CXF wsdl2java generated interface:

/*
 * 
 */

package org.apache.camel.example.reportincident;

import javax.jws.WebMethod;
import javax.jws.WebParam;
import javax.jws.WebResult;
import javax.jws.WebService;
import javax.jws.soap.SOAPBinding;
import javax.jws.soap.SOAPBinding.ParameterStyle;
import javax.xml.bind.annotation.XmlSeeAlso;

/**
 * This class was generated by Apache CXF 2.1.1
 * Wed Jul 16 12:40:31 CEST 2008
 * Generated source version: 2.1.1
 * 
 */
 
 /*
  * 
  */


@WebService(targetNamespace = "http://reportincident.example.camel.apache.org", name = "ReportIncidentEndpoint")
@XmlSeeAlso({ObjectFactory.class})
@SOAPBinding(parameterStyle = SOAPBinding.ParameterStyle.BARE)

public interface ReportIncidentEndpoint {

/*
 * 
 */

    @SOAPBinding(parameterStyle = SOAPBinding.ParameterStyle.BARE)
    @WebResult(name = "outputReportIncident", targetNamespace = "http://reportincident.example.camel.apache.org", partName = "parameters")
    @WebMethod(operationName = "ReportIncident", action = "http://reportincident.example.camel.apache.org/ReportIncident")
    public OutputReportIncident reportIncident(
        @WebParam(partName = "parameters", name = "inputReportIncident", targetNamespace = "http://reportincident.example.camel.apache.org")
        InputReportIncident parameters
    );
}

Next up is to create a webservice client so we can invoke our webservice. For this we actually use the CXF framework directly as its a bit more easier to create a client using this framework than using the JAXWS style. We could have done the same for the server part, and you should do this if you need more power and access more advanced features.

    import org.apache.cxf.jaxws.JaxWsProxyFactoryBean;
    ...
    
    protected ReportIncidentEndpoint createCXFClient() {
        // we use CXF to create a client for us as its easier than JAXWS and works
        JaxWsProxyFactoryBean factory = new JaxWsProxyFactoryBean();
        factory.setServiceClass(ReportIncidentEndpoint.class);
        factory.setAddress(ADDRESS);
        return (ReportIncidentEndpoint) factory.create();
    }

So now we are ready for creating a unit test. We have the server and the client. So we just create a plain simple unit test method as the usual junit style:

    public void testRendportIncident() throws Exception {
        startServer();

        ReportIncidentEndpoint client = createCXFClient();

        InputReportIncident input = new InputReportIncident();
        input.setIncidentId("123");
        input.setIncidentDate("2008-07-16");
        input.setGivenName("Claus");
        input.setFamilyName("Ibsen");
        input.setSummary("bla bla");
        input.setDetails("more bla bla");
        input.setEmail("davsclaus@apache.org");
        input.setPhone("+45 2962 7576");

        OutputReportIncident out = client.reportIncident(input);
        assertEquals("Response code is wrong", "OK", out.getCode());
    }

Now we are nearly there. But if you run the unit test with mvn test then it will fail. Why!!! Well its because that CXF needs is missing some dependencies during unit testing. In fact it needs the web container, so we need to add this to our pom.xml.

    <!-- cxf web container for unit testing -->
    <dependency>
        <groupId>org.apache.cxf</groupId>
        <artifactId>cxf-rt-transports-http-jetty</artifactId>
        <version>${cxf-version}</version>
        <scope>test</scope>
    </dependency>

Well what is that, CXF also uses Jetty for unit test - well its just shows how agile, embedable and popular Jetty is.

So lets run our junit test with, and it reports:

mvn test
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
[INFO] BUILD SUCCESSFUL

Yep thats it for now. We have a basic project setup.

End of part 1

Thanks for being patient and reading all this more or less standard Maven, Spring, JAXWS and Apache CXF stuff. Its stuff that is well covered on the net, but I wanted a full fledged tutorial on a maven project setup that is web service ready with Apache CXF. We will use this as a base for the next part where we demonstrate how Camel can be digested slowly and piece by piece just as it was back in the times when was introduced and was learning the Spring framework that we take for granted today.

#Resources

• Apache CXF user guide

Links

• Introduction
• Part 1
• Part 2
• Part 3
• Part 4
• Part 5
• Part 6

Part 2

Adding Camel

In this part we will introduce Camel so we start by adding Camel to our pom.xml:

       <properties>
            ...
            <camel-version>1.4.0</camel-version>
        </properties>

        <!-- camel -->
        <dependency>
            <groupId>org.apache.camel</groupId>
            <artifactId>camel-core</artifactId>
            <version>${camel-version}</version>
        </dependency>

That's it, only one dependency for now.

Now we turn towards our webservice endpoint implementation where we want to let Camel have a go at the input we receive. As Camel is very non invasive its basically a .jar file then we can just grap Camel but creating a new instance of DefaultCamelContext that is the hearth of Camel its context.

CamelContext camel = new DefaultCamelContext();

In fact we create a constructor in our webservice and add this code:

    private CamelContext camel;

    public ReportIncidentEndpointImpl() throws Exception {
        // create the camel context that is the "heart" of Camel
        camel = new DefaultCamelContext();

        // add the log component
        camel.addComponent("log", new LogComponent());

        // start Camel
        camel.start();
    }

Logging the "Hello World"

Here at first we want Camel to log the givenName and familyName parameters we receive, so we add the LogComponent with the key log. And we must start Camel before its ready to act.

Then we change the code in the method that is invoked by Apache CXF when a webservice request arrives. We get the name and let Camel have a go at it in the new method we create sendToCamel:

    public OutputReportIncident reportIncident(InputReportIncident parameters) {
        String name = parameters.getGivenName() + " " + parameters.getFamilyName();

        // let Camel do something with the name
        sendToCamelLog(name);

        OutputReportIncident out = new OutputReportIncident();
        out.setCode("OK");
        return out;
    }

Next is the Camel code. At first it looks like there are many code lines to do a simple task of logging the name - yes it is. But later you will in fact realize this is one of Camels true power. Its concise API. Hint: The same code can be used for any component in Camel.

    private void sendToCamelLog(String name) {
        try {
            // get the log component
            Component component = camel.getComponent("log");

            // create an endpoint and configure it.
            // Notice the URI parameters this is a common pratice in Camel to configure
            // endpoints based on URI.
            // com.mycompany.part2 = the log category used. Will log at INFO level as default
            Endpoint endpoint = component.createEndpoint("log:com.mycompany.part2");

            // create an Exchange that we want to send to the endpoint
            Exchange exchange = endpoint.createExchange();
            // set the in message payload (=body) with the name parameter
            exchange.getIn().setBody(name);

            // now we want to send the exchange to this endpoint and we then need a producer
            // for this, so we create and start the producer.
            Producer producer = endpoint.createProducer();
            producer.start();
            // process the exchange will send the exchange to the log component, that will process
            // the exchange and yes log the payload
            producer.process(exchange);

            // stop the producer, we want to be nice and cleanup
            producer.stop();




        } catch (Exception e) {
            // we ignore any exceptions and just rethrow as runtime
            throw new RuntimeException(e);

        }
    }

Okay there are code comments in the code block above that should explain what is happening. We run the code by invoking our unit test with maven mvn test, and we should get this log line:

INFO: Exchange[BodyType:String, Body:Claus Ibsen]

Write to file - easy with the same code style

Okay that isn't to impressive, Camel can log Well I promised that the above code style can be used for any component, so let's store the payload in a file. We do this by adding the file component to the Camel context

        // add the file component
        camel.addComponent("file", new FileComponent());

And then we let camel write the payload to the file after we have logged, by creating a new method sendToCamelFile. We want to store the payload in filename with the incident id so we need this parameter also:

        // let Camel do something with the name
        sendToCamelLog(name);
        sendToCamelFile(parameters.getIncidentId(), name);

And then the code that is 99% identical. We have change the URI configuration when we create the endpoint as we pass in configuration parameters to the file component.
And then we need to set the output filename and this is done by adding a special header to the exchange. That's the only difference:

    private void sendToCamelFile(String incidentId, String name) {
        try {
            // get the file component
            Component component = camel.getComponent("file");

            // create an endpoint and configure it.
            // Notice the URI parameters this is a common pratice in Camel to configure
            // endpoints based on URI.
            // file://target instructs the base folder to output the files. We put in the target folder
            // then its actumatically cleaned by mvn clean
            Endpoint endpoint = component.createEndpoint("file://target");

            // create an Exchange that we want to send to the endpoint
            Exchange exchange = endpoint.createExchange();
            // set the in message payload (=body) with the name parameter
            exchange.getIn().setBody(name);

            // now a special header is set to instruct the file component what the output filename
            // should be
            exchange.getIn().setHeader(FileComponent.HEADER_FILE_NAME, "incident-" + incidentId + ".txt");

            // now we want to send the exchange to this endpoint and we then need a producer
            // for this, so we create and start the producer.
            Producer producer = endpoint.createProducer();
            producer.start();
            // process the exchange will send the exchange to the file component, that will process
            // the exchange and yes write the payload to the given filename
            producer.process(exchange);

            // stop the producer, we want to be nice and cleanup
            producer.stop();
        } catch (Exception e) {
            // we ignore any exceptions and just rethrow as runtime
            throw new RuntimeException(e);
        }
    }

After running our unit test again with mvn test we have a output file in the target folder:

D:\demo\part-two>type target\incident-123.txt
Claus Ibsen

Fully java based configuration of endpoints

In the file example above the configuration was URI based. What if you want 100% java setter based style, well this is of course also possible. We just need to cast to the component specific endpoint and then we have all the setters available:

            // create the file endpoint, we cast to FileEndpoint because then we can do
            // 100% java settter based configuration instead of the URI sting based
            // must pass in an empty string, or part of the URI configuration if wanted 
            FileEndpoint endpoint = (FileEndpoint)component.createEndpoint("");
            endpoint.setFile(new File("target/subfolder"));
            endpoint.setAutoCreate(true);

That's it. Now we have used the setters to configure the FileEndpoint that it should store the file in the folder target/subfolder. Of course Camel now stores the file in the subfolder.

D:\demo\part-two>type target\subfolder\incident-123.txt
Claus Ibsen

Lessons learned

Okay I wanted to demonstrate how you can be in 100% control of the configuration and usage of Camel based on plain Java code with no hidden magic or special XML or other configuration files. Just add the camel-core.jar and you are ready to go.

You must have noticed that the code for sending a message to a given endpoint is the same for both the log and file, in fact any Camel endpoint. You as the client shouldn't bother with component specific code such as file stuff for file components, jms stuff for JMS messaging etc. This is what the Message Endpoint EIP pattern is all about and Camel solves this very very nice - a key pattern in Camel.

Reducing code lines

Now that you have been introduced to Camel and one of its masterpiece patterns solved elegantly with the Message Endpoint its time to give productive and show a solution in fewer code lines, in fact we can get it down to 5, 4, 3, 2 .. yes only 1 line of code.

The key is the ProducerTemplate that is a Spring'ish xxxTemplate based producer. Meaning that it has methods to send messages to any Camel endpoints. First of all we need to get hold of such a template and this is done from the CamelContext

    private ProducerTemplate template;

    public ReportIncidentEndpointImpl() throws Exception {
        ...

        // get the ProducerTemplate thst is a Spring'ish xxxTemplate based producer for very
        // easy sending exchanges to Camel.
        template = camel.createProducerTemplate();

        // start Camel
        camel.start();
    }

Now we can use template for sending payloads to any endpoint in Camel. So all the logging gabble can be reduced to:

    template.sendBody("log:com.mycompany.part2.easy", name);

And the same goes for the file, but we must also send the header to instruct what the output filename should be:

    String filename = "easy-incident-" + incidentId + ".txt";
    template.sendBodyAndHeader("file://target/subfolder", name, FileComponent.HEADER_FILE_NAME, filename);

Reducing even more code lines

Well we got the Camel code down to 1-2 lines for sending the message to the component that does all the heavy work of wring the message to a file etc. But we still got 5 lines to initialize Camel.

    camel = new DefaultCamelContext();
    camel.addComponent("log", new LogComponent());
    camel.addComponent("file", new FileComponent());
    template = camel.createProducerTemplate();
    camel.start();

This can also be reduced. All the standard components in Camel is auto discovered on-the-fly so we can remove these code lines and we are down to 3 lines.

class=org.apache.camel.component.log.LogComponent

Okay back to the 3 code lines:

    camel = new DefaultCamelContext();
    template = camel.createProducerTemplate();
    camel.start();

Later will we see how we can reduce this to ... in fact 0 java code lines. But the 3 lines will do for now.

Message Translation

Okay lets head back to the over goal of the integration. Looking at the EIP diagrams at the introduction page we need to be able to translate the incoming webservice to an email. Doing so we need to create the email body. When doing the message translation we could put up our sleeves and do it manually in pure java with a StringBuilder such as:

    private String createMailBody(InputReportIncident parameters) {
        StringBuilder sb = new StringBuilder();
        sb.append("Incident ").append(parameters.getIncidentId());
        sb.append(" has been reported on the ").append(parameters.getIncidentDate());
        sb.append(" by ").append(parameters.getGivenName());
        sb.append(" ").append(parameters.getFamilyName());
        
        // and the rest of the mail body with more appends to the string builder
        
        return sb.toString();
    }

But as always it is a hardcoded template for the mail body and the code gets kinda ugly if the mail message has to be a bit more advanced. But of course it just works out-of-the-box with just classes already in the JDK.

Lets use a template language instead such as Apache Velocity. As Camel have a component for Velocity integration we will use this component. Looking at the Component List overview we can see that camel-velocity component uses the artifactId camel-velocity so therefore we need to add this to the pom.xml

        <dependency>
            <groupId>org.apache.camel</groupId>
            <artifactId>camel-velocity</artifactId>
            <version>${camel-version}</version>
        </dependency>

And now we have a Spring conflict as Apache CXF is dependent on Spring 2.0.8 and camel-velocity is dependent on Spring 2.5.5. To remedy this we could wrestle with the pom.xml with excludes settings in the dependencies or just bring in another dependency camel-spring:

        <dependency>
            <groupId>org.apache.camel</groupId>
            <artifactId>camel-spring</artifactId>
            <version>${camel-version}</version>
        </dependency>

In fact camel-spring is such a vital part of Camel that you will end up using it in nearly all situations - we will look into how well Camel is seamless integration with Spring in part 3. For now its just another dependency.

We create the mail body with the Velocity template and create the file src/main/resources/MailBody.vm. The content in the MailBody.vm file is: