Author: Nevin Zhu
Level: Intermediate
Technologies: CDI, Servlet, JSP
Summary: The cdi-alternative
quickstart demonstrates how to create a bean that can be implemented for different purposes without changing the source code.
Target Product: WildFly
Source: https://github.com/wildfly/quickstart/
The cdi-alternative
quickstart demonstrates how to create beans that can be implemented for different purposes in WildFly Application Server without changing the Java source code. Instead, you define the default and alternative (@Alternative
) bean implementations during the development phase. Then at deployment time, rather than modifying the source code, you can choose to deploy the default or alternative beans by modifying the <alternatives>
element in the WEB-INF/beans.xml
file.
Alternatives can be used to customize deployments for specific situations, to handle client-side business logic that is determined at runtime, and to create dummy beans to be used for test purposes.
This quickstart demonstrates how to deploy an example with alternative sales tax rates. It defines the following classes, interfaces, and WEB-INF/beans.xml
files:
Demo
: This class extends HttpServlet
and handles the incoming servlet request. It gets the tax rate and returns it to the page.Tax
: This interface defines the getRate()
method to get the tax rate.TaxImpl_1
: This is the default class that returns the Tax_1
rate.TaxImpl_2
: This is an alternative class that returns the Tax_2
rate. Note the @Alternative
annotation in the class.WEB-INF/beans.xml
: This file specifies the TaxImpl_2
alternative should be used by the quickstart. To use the default TaxImpl_1
class, delete or comment out the <alternatives>
element and redeploy the quickstart.result.jsp
: The JSP page that displays the tax rate.The application this project produces is designed to be run on WildFly Application Server 11 or later.
All you need to build this project is Java 8.0 (Java SDK 1.8) or later and Maven 3.3.1 or later. See Configure Maven for WildFly 11 to make sure you are configured correctly for testing the quickstarts.
In the following instructions, replace WILDFLY_HOME
with the actual path to your WildFly installation. The installation path is described in detail here: Use of WILDFLY_HOME and JBOSS_HOME Variables.
For Linux: WILDFLY_HOME/bin/standalone.sh
For Windows: WILDFLY_HOME\bin\standalone.bat
mvn clean install wildfly:deploy
This deploys target/cdi-alternative.war
to the running instance of the server.
The application will be running at the following URL: http://localhost:8080/cdi-alternative/.
You can specify alternative versions of the bean in the WEB-INF/beans.xml
file by doing one of the following:
<alternatives>
tag so that it defaults to use TaxImpl_1
.In this quickstart, in order to switch back to the default implementation, comment the <alternatives>
block in the WEB-INF/beans.xml
file and redeploy the quickstart.
mvn wildfly:undeploy
You can also start the server and deploy the quickstarts or run the Arquillian tests from Eclipse using JBoss tools. For general information about how to import a quickstart, add a WildFly server, and build and deploy a quickstart, see Use JBoss Developer Studio or Eclipse to Run the Quickstarts.
If you want to debug the source code of any library in the project, run the following command to pull the source into your local repository. The IDE should then detect it.
mvn dependency:sources