[[Remote_EJB_invocations_via_JNDI_-_EJB_client_API_or_remote-naming_project]]
= Remote EJB invocations via JNDI - EJB client API or remote-naming project

[[purpose]]
== Purpose

WildFly provides EJB client API project as well as remote-naming project
for invoking on remote objects exposed via JNDI. This article explains
which approach to use when and what the differences and scope of each of
these projects is.

[[history]]
== History

Previous versions of JBoss AS (versions < WildFly {wildflyVersion}) used JNP project (
http://anonsvn.jboss.org/repos/jbossas/projects/naming/) as the JNDI
naming implementation. Developers of client applications of previous
versions of JBoss AS will be familiar with the `jnp:// PROVIDER_URL` URL
they used to use in their applications for communicating with the JNDI
server on the JBoss server.

Starting WildFly {wildflyVersion}, the JNP project is _not_ used. Neither on the server
side nor on the client side. The client side of the JNP project has now
been replaced by jboss-remote-naming project (
https://github.com/jbossas/jboss-remote-naming). There were various
reasons why the JNP client was replaced by jboss-remote-naming project.
One of them was the JNP project did not allow fine grained security
configurations while communicating with the JNDI server. The
jboss-remote-naming project is backed by the jboss-remoting project (
https://github.com/jboss-remoting/jboss-remoting) which allows much more
and better control over security.

[[overview]]
== Overview

Now that we know that for remote client JNDI communication with WildFly
8 requires jboss-remote-naming project, let's quickly see what the code
looks like.

[[client-code-relying-on-jndi.properties-in-classpath]]
=== Client code relying on jndi.properties in classpath

[source, java]
----
void doLookup() {
  // Create an InitialContext using the javax.naming.* API
  Context ctx = new InitialContext();
  ctx.lookup("foo/bar");
  ...
}
----

As you can see, there's not much here in terms of code. We first create
a InitialContext (
http://download.oracle.com/javase/6/docs/api/javax/naming/InitialContext.html)
which as per the API will look for a jndi.properties in the classpath of
the application. We'll see what our jndi.properties looks like, later.
Once the InitialContext is created, we just use it to do a lookup on a
JNDI name which we know is bound on the server side. We'll come back to
the details of this lookup string in a while.

Let's now see what the jndi.properties in our client classpath looks
like:

[source, java]
----
java.naming.factory.initial=org.jboss.naming.remote.client.InitialContextFactory
java.naming.provider.url=http-remoting://localhost:8080
----

Those 2 properties are important for jboss-remote-naming project to be
used for communicating with the WildFly server. The first property tells
the JNDI API which initial context factory to use. In this case we are
pointing it to the InitailContextFactory class supplied by the
jboss-remote-naming project. The other property is the PROVIDER_URL.
Developers familiar with previous JBoss AS versions would remember that
they used `jnp://localhost:1099` (just an example). In WildFly, the URI
protocol scheme for jboss-remote-naming project is `remote://`. The rest
of the PROVIDER_URL part is the server hostname or IP and the port on
which the remoting connector is exposed on the server side. By default
the http-remoting connector port in WildFly {wildflyVersion} is 8080. That's what we
have used in our example. The hostname we have used is localhost but
that should point to the server IP or hostname where the server is
running.

[NOTE]

JNP client project in previous AS versions allowed a comma separated
list for PROVIDER_URL value, so that if one of the server isn't
accessible then the JNDI API would use the next available server. The
jboss-remote-naming project has similar support starting 1.0.3.Final
version of that project (which is available in a WildFly release *after*
7.1.1.Final).

WildFly {wildflyVersion} can use the PROVIDER_URL like:

java.naming.provider.url=http-remoting://server1:8080,http-remoting://server2:8080

So we saw how to setup the JNDI properties in the jndi.properties file.
The JNDI API also allows you to pass these properties to the constructor
of the InitialContext class (please check the javadoc of that class for
more details). Let's quickly see what the code would look like:

[source, java]
----
void doLookup() {
  Properties jndiProps = new Properties();
  jndiProps.put(Context.INITIAL_CONTEXT_FACTORY, "org.jboss.naming.remote.client.InitialContextFactory");
  jndiProps.put(Context.PROVIDER_URL,"http-remoting://localhost:8080");
  // create a context passing these properties
  Context ctx = new InitialContext(jndiProps);
  // lookup
  ctx.lookup("foo/bar");
  ...
}
----

That's it! You can see that the values that we pass to those properties
are the same as what we did via the jndi.properties. It's upto the
client application to decide which approach they want to follow.

[[how-does-remoting-naming-work]]
=== How does remoting naming work

We have so far had an overview of how the client code looks like when
using the jboss-remote-naming (henceforth referred to as remote-naming -
too tired of typing jboss-remote-naming everytime icon:smile-o[role="yellow"]
) project. Let's now have a brief look at how the remote-naming project
internally establishes the communication with the server and allows JNDI
operations from the client side.

Like previously mentioned, remote-naming internally uses jboss-remoting
project. When the client code creates an InitialContext backed by the
org.jboss.naming.remote.client.InitialContextFactory class, the
`org.jboss.naming.remote.client.InitialContextFactory` internally looks
for the PROVIDER_URL (and other) properties that are applicable for that
context ( _doesn't_ matter whether it comes from the jndi.properties
file or whether passed explicitly to the constructor of the
InitialContext). Once it identifies the server and port to connect to,
the remote-naming project internally sets up a connection using the
jboss-remoting APIs with the remoting connector which is exposed on that
port.

We previously mentioned that remote-naming, backed by jboss-remoting
project, has increased support for security configurations. Starting
WildFly {wildflyVersion}, every service including the http remoting connector (which
listens by default on port 8080), is secured (see
https://community.jboss.org/wiki/AS710Beta1-SecurityEnabledByDefault for
details). This means that when trying to do JNDI operations like a
lookup, the client has to pass appropriate user credentials. In our
examples so far we haven't passed any username/pass or any other
credentials while creating the InitialContext. That was just to keep the
examples simple. But let's now take the code a step further and see one
of the ways how we pass the user credentials. Let's at the moment just
assume that the remoting connector on port 8080 is accessible to a user
named " `peter`" whose password is expected to be " `lois`".

[NOTE]

Note: The server side configurations for the remoting connector to allow
"peter" to access the connector, is out of the scope of this
documentation. The WildFly {wildflyVersion} documentation already has chapters on how
to set that up.

[source, java]
----
void doLookup() {
  Properties jndiProps = new Properties();
  jndiProps.put(Context.INITIAL_CONTEXT_FACTORY, "org.jboss.naming.remote.client.InitialContextFactory");
  jndiProps.put(Context.PROVIDER_URL,"http-remoting://localhost:8080");
  // username
  jndiProps.put(Context.SECURITY_PRINCIPAL, "peter");
  // password
  jndiProps.put(Context.SECURITY_CREDENTIALS, "lois");
  // create a context passing these properties
  Context ctx = new InitialContext(jndiProps);
  // lookup
  ctx.lookup("foo/bar");
  ...
}
----

The code is similar to our previous example, except that we now have
added 2 additional properties that are passed to the InitialContext
constructor. The first is
http://docs.oracle.com/javase/6/docs/api/javax/naming/Context.html#SECURITY_PRINCIPAL
which passes the username (peter in this case) and the second is
http://docs.oracle.com/javase/6/docs/api/javax/naming/Context.html#SECURITY_CREDENTIALS
which passes the password (lois in this case). Of course the same
properties can be configured in the jndi.properties file (read the
javadoc of the Context class for appropriate properties to be used in
the jndi.properties). This is one way of passing the security
credentials for JNDI communication with WildFly. There are some other
ways to do this too. But we won't go into those details here for two
reasons. One, it's outside the scope of this article and two (which is
kind of the real reason) I haven't looked fully at the remote-naming
implementation details to see what other ways are allowed.

[[jndi-operations-allowed-using-remote-naming-project]]
=== JNDI operations allowed using remote-naming project

So far we have mainly concentrated on how the naming context is created
and what it internally does when an instance is created. Let's now take
this one step further and see what kind of operations are allowed for a
JNDI context backed by the remote-naming project.

The JNDI Context has various methods
http://docs.oracle.com/javase/6/docs/api/javax/naming/Context.html that
are exposed for JNDI operations. One important thing to note in case of
remote-naming project is that, the project's scope is to allow a client
to communicate with the JNDI backend exposed by the server. As such, the
remote-naming project does *not* support many of the methods that are
exposed by the javax.naming.Context class. The remote-naming project
only supports the read-only kind of methods (like the lookup() method)
and does not support any write kind of methods (like the bind() method).
The client applications are expected to use the remote-naming project
mainly for lookups of JNDI objects. Neither WildFly {wildflyVersion} nor remote-naming
project allows writing/binding to the JNDI server from a remote
application.

[[pre-requisites-of-remotely-accessible-jndi-objects]]
=== Pre-requisites of remotely accessible JNDI objects

On the server side, the JNDI can contain numerous objects that are bound
to it. However, _not_ all of those are exposed remotely. The two
conditions that are to be satisfied by the objects bound to JNDI, to be
remotely accessible are:

1) Such objects should be bound under the `java:jboss/exported/`
namespace. For example, `java:jboss/exported/foo/bar` +
2) Objects bound to the `java:jboss/exported/` namespace are expected to
be serializable. This allows the objects to be sent over the wire to the
remote clients

Both these conditions are important and are required for the objects to
be remotely accessible via JNDI.

[[jndi-lookup-strings-for-remote-clients-backed-by-the-remote-naming-project]]
=== JNDI lookup strings for remote clients backed by the remote-naming
project

In our examples, so far, we have been consistently using " `foo/bar`" as
the JNDI name to lookup from a remote client using the remote-naming
project. There's a bit more to understand about the JNDI name and how it
maps to the JNDI name that's bound on the server side.

First of all, the JNDI names used while using the remote-naming project
are *always* relative to the java:jboss/exported/ namespace. So in our
examples, we are using " `foo/bar`" JNDI name for the lookup, that
actually is (internally) " `java:jboss/exported/foo/bar`". The
remote-naming project expects it to *always* be relative to the "
`java:jboss/exported/`" namespace. Once connected with the server side,
the remote-naming project will lookup for "foo/bar" JNDI name under the
" `java:jboss/exported/`" namespace of the server.

[NOTE]

Note: Since the JNDI name that you use on the client side is *always*
relative to java:jboss/exported namespace, you *shouldn't* be prefixing
the java:jboss/exported/ string to the JNDI name. For example, if you
use the following JNDI name:

ctx.lookup("java:jboss/exported/helloworld");

then remote-naming will translate it to

ctx.lookup("java:jboss/exported/java:jboss/exported/helloworld");

and as a result, will fail during lookup.

The remote-naming implementation perhaps should be smart enough to strip
off the java:jboss/exported/ namespace prefix if supplied. But let's not
go into that here.

[[how-does-remote-naming-project-implementation-transfer-the-jndi-objects-to-the-clients]]
=== How does remote-naming project implementation transfer the JNDI
objects to the clients

When a lookup is done on a JNDI string, the remote-naming implementation
internally uses the connection to the remoting connector (which it has
established based on the properties that were passed to the
InitialContext) to communicate with the server. On the server side, the
implementation then looks for the JNDI name under the
`java:jboss/exported/` namespace. Assuming that the JNDI name is
available, under that namespace, the remote-naming implementation then
passes over the object bound at that address to the client. This is
where the requirement about the JNDI object being serializable comes
into picture. remote-naming project internally uses jboss-marshalling
project to marshal the JNDI object over to the client. On the client
side the remote-naming implementation then unmarshalles the object and
returns it to the client application.

So literally, each lookup backed by the remote-naming project entails a
server side communication/interaction and then marshalling/unmarshalling
of the object graph. This is very important to remember. We'll come back
to this later, to see why this is important when it comes to using EJB
client API project for doing EJB lookups ( <<EJB_invocations_from_a_remote_client_using_JNDI,EJB
invocations from a remote client using JNDI>>) as against using
remote-naming project for doing the same thing.

[[summary]]
== Summary

That pretty much covers whatever is important to know, in the
remote-naming project, for a typical client application. Don't close the
browser yet though, since we haven't yet come to the part of EJB
invocations from a remote client using the remote-naming project. In
fact, the motivation behind writing this article was to explain why
_not_ to use remote-naming project (in most cases) for doing EJB
invocations against WildFly server.

Those of you who don't have client applications doing remote EJB
invocations, can just skip the rest of this article if you aren't
interested in those details.

[[remote-ejb-invocations-backed-by-the-remote-naming-project]]
== Remote EJB invocations backed by the remote-naming project

In previous sections of this article we saw that whatever is exposed in
the java:jboss/exported/ namespace is accessible remotely to the client
applications under the relative JNDI name. Some of you might already
have started thinking about exposing remote views of EJBs under that
namespace.

It's important to note that WildFly server side already by default
exposes the remote views of a EJB under the `java:jboss/exported/`
namespace (although it isn't logged in the server logs). So assuming
your server side application has the following stateless bean:

[source, java]
----
package org.myapp.ejb;
 
@Stateless
@Remote(Foo.class)
public class FooBean implements Foo {
...
 public String sayBar() {
     return "Baaaaaaaar";
 }
}
----

Then the " `Foo`" remote view is exposed under the
`java:jboss/exported/` namespace under the following JNDI name scheme
(which is similar to that mandated by EJB3.1 spec for `java:global/`
namespace):
link:/pages/createpage.action?spaceKey=WFLY&title=app-name&linkCreation=true&fromPageId=557285[app-name]

`app-name/module-name/bean-name!bean-interface`

where,

`app-name` = the name of the .ear (without the .ear suffix) or the
application name configured via application.xml deployment descriptor.
If the application isn't packaged in a .ear then there will be *no*
app-name part to the JNDI string. +
`module-name` = the name of the .jar or .war (without the .jar/.war
suffix) in which the bean is deployed or the module-name configured in
web.xml/ejb-jar.xml of the deployment. The module name is mandatory part
in the JNDI string. +
`bean-name` = the name of the bean which by default is the simple name
of the bean implementation class. Of course it can be overridden either
by using the "name" attribute of the bean definining annotation
(@Stateless(name="blah") in this case) or even the ejb-jar.xml
deployment descriptor. +
`bean-interface` = the fully qualified class name of the interface being
exposed by the bean.

So in our example above, let's assume the bean is packaged in a
myejbmodule.jar which is within a myapp.ear. So the JNDI name for the
Foo remote view under the `java:jboss/exported/` namespace would be:

`java:jboss/exported/myapp/myejbmodule/FooBean!org.myapp.ejb.Foo`

That's where WildFly will *automatically* expose the remote views of the
EJBs under the `java:jboss/exported/` namespace, *in addition to* the
java:global/ java:app/ java:module/ namespaces mandated by the EJB 3.1
spec.

[NOTE]

Note that only the java:jboss/exported/ namespace is available to remote
clients.

So the next logical question would be, are these remote views of EJBs
accessible and invokable using the remote-naming project on the client
application. The answer is _yes_! Let's quickly see the client code for
invoking our `FooBean`. Again, let's just use " `peter`" and " `lois`"
as username/pass for connecting to the remoting connector.

[source, java]
----
void doBeanLookup() {
  ...
  Properties jndiProps = new Properties();
  jndiProps.put(Context.INITIAL_CONTEXT_FACTORY, "org.jboss.naming.remote.client.InitialContextFactory");
  jndiProps.put(Context.PROVIDER_URL,"http-remoting://localhost:8080");
  // username
  jndiProps.put(Context.SECURITY_PRINCIPAL, "peter");
  // password
  jndiProps.put(Context.SECURITY_CREDENTIALS, "lois");
  // This is an important property to set if you want to do EJB invocations via the remote-naming project
  jndiProps.put("jboss.naming.client.ejb.context", true);
  // create a context passing these properties
  Context ctx = new InitialContext(jndiProps);
  // lookup the bean     Foo
  beanRemoteInterface = (Foo) ctx.lookup("myapp/myejbmodule/FooBean!org.myapp.ejb.Foo");
  String bar = beanRemoteInterface.sayBar();
  System.out.println("Remote Foo bean returned " + bar);
  ctx.close();
  // after this point the beanRemoteInterface is not longer valid!
}
----

As you can see, most of the code is similar to what we have been seeing
so far for setting up a JNDI context backed by the remote-naming
project. The only parts that change are:

\1) An additional " `jboss.naming.client.ejb.context`" property that is
added to the properties passed to the InitialContext constructor. +
2) The JNDI name used for the lookup +
3) And subsequently the invocation on the bean interface returned by the
lookup.

Let's see what the " `jboss.naming.client.ejb.context`" does. In
WildFly, remote access/invocations on EJBs is facilitated by the JBoss
specific EJB client API, which is a project on its own
https://github.com/jbossas/jboss-ejb-client. So no matter, what
mechanism you use (remote-naming or core EJB client API), the
invocations are ultimately routed through the EJB client API project. In
this case too, the remote-naming internally uses EJB client API to
handle EJB invocations. From a EJB client API project perspective, for
successful communication with the server, the project expects a
`EJBClientContext` backed by (atleast one) `EJBReceiver`(s). The
`EJBReceiver` is responsible for handling the EJB invocations. One type
of a `EJBReceiver` is a `RemotingConnectionEJBReceiver` which internally
uses jboss-remoting project to communicate with the remote server to
handle the EJB invocations. Such a `EJBReceiver` expects a connection
backed by the jboss-remoting project. Of course to be able to connect to
the server, such a `EJBReceiver` would have to know the server address,
port, security credentials and other similar parameters. If you were
using the core EJB client API, then you would have configured all these
properties via the jboss-ejb-client.properties or via programatic API
usage as explained here <<EJB_invocations_from_a_remote_client_using_JNDI,EJB invocations from a remote
client using JNDI>>. But in the example above, we are using remote-naming
project and are _not_ directly interacting with the EJB client API
project.

If you look closely at what's being passed, via the JNDI properties, to
the remote-naming project and if you remember the details that we
explained in a previous section about how the remote-naming project
establishes a connection to the remote server, you'll realize that these
properties are indeed the same as what the
`RemotingConnectionEJBReceiver` would expect to be able to establish the
connection to the server. Now this is where the "
`jboss.naming.client.ejb.context`" property comes into picture. When
this is set to true and passed to the InitialContext creation (either
via jndi.properties or via the constructor of that class), the
remote-naming project internally will do whatever is necessary to setup
a `EJBClientContext`, containing a `RemotingConnectionEJBReceiver` which
is created using the *same* remoting connection that is created by and
being used by remote-naming project for its own JNDI communication
usage. So effectively, the InitialContext creation via the remote-naming
project has now internally triggered the creation of a
`EJBClientContext` containing a `EJBReceiver` capable of handling the
EJB invocations (remember, no remote EJB invocations are possible
without the presence of a `EJBClientContext` containing a `EJBReceiver`
which can handle the EJB).

So we now know the importance of the "
`jboss.naming.client.ejb.context`" property and its usage. Let's move on
the next part in that code, the JNDI name. Notice that we have used the
JNDI name relative to the `java:jboss/exported/` namespace while doing
the lookup. And since we know that the Foo view is exposed on that JNDI
name, we cast the returned object back to the Foo interface. Remember
that we earlier explained how each lookup via remote-naming triggers a
server side communication and a marshalling/unmarshalling process. This
applies for EJB views too. In fact, the remote-naming project has no
clue (since that's not in the scope of that project to know) whether
it's an EJB or some random object.

Once the unmarshalled object is returned (which actually is a proxy to
the bean), the rest is straightforward, we just invoke on that returned
object. Now since the remote-naming implementation has done the
necessary setup for the EJBClientContext (due to the presence of "
`jboss.naming.client.ejb.context`" property), the invocation on that
proxy will internally use the `EJBClientContext` (the proxy is smart
enough to do that) to interact with the server and return back the
result. We won't go into the details of how the EJB client API handles
the communication/invocation.

_Long story short, using the remote-naming project for doing remote EJB
invocations against WildFly is possible!_

[[why-use-the-ejb-client-api-approach-then]]
== Why use the EJB client API approach then?

I can guess that some of you might already question why/when would one
use the EJB client API style lookups as explained in the
<<EJB_invocations_from_a_remote_client_using_JNDI,EJB invocations from a remote client using JNDI>>
article instead of just using (what appears to be a simpler)
remote-naming style lookups.

Before we answer that, let's understand a bit about the EJB client
project. The EJB client project was implemented keeping in mind various
optimizations and features that would be possible for handling remote
invocations. One such optimization was to avoid doing unnecessary server
side communication(s) which would typically involve network calls,
marshalling/unmarshalling etc... The easiest place where this
optimization can be applied, is to the EJB lookup. Consider the
following code (let's ignore how the context is created):

[source, java]
----
ctx.lookup("foo/bar");
----

Now `foo/bar` JNDI name could potentially point to *any* type of object
on the server side. The jndi name itself won't have the type/semantic
information of the object bound to that name on the server side. If the
context was setup using the remote-naming project (like we have seen
earlier in our examples), then the only way for remote-naming to return
an object for that lookup operation is to communicate with the server
and marshal/unmarshal the object bound on the server side. And that's
exactly what it does (remember, we explained this earlier).

The EJB client API project on the other hand optimizes this lookup. In
order to do so, it expects the client application to let it know that a
EJB is being looked up. It does this, by expecting the client
application to use the JNDI name of the format " `ejb:`" namespace and
also expecting the client application to setup the JNDI context by
passing the " `org.jboss.ejb.client.naming`" value for the
`Context.URL_PKG_PREFIXES` property.

Example:

[source, java]
----
final Properties jndiProperties = new Properties();
jndiProperties.put(Context.URL_PKG_PREFIXES, "org.jboss.ejb.client.naming");
// create the context
final Context context = new InitialContext(jndiProperties);
 
// lookup
Foo beanProxy = context.lookup("ejb:myapp/myejbmodule//FooBean!org.myapp.ejb.Foo");
String bar = beanProxy.sayBar();
----

More details about such code can be found here <<EJB_invocations_from_a_remote_client_using_JNDI,EJB
invocations from a remote client using JNDI>>

When a client application looks up anything under the " `ejb:`"
namespace, it is a clear indication (for the EJB client API project) to
know that the client is looking up an EJB. That's where it steps in to
do the necessary optimizations that might be applicable. So unlike, in
the case of remote-naming project (which has no clue about the semantics
of the object being looked up), the EJB client API project does *not*
trigger a server side communication or a marshal/unmarshal process when
you do lookup for a remote view of a stateless bean (it's important to
note that we have specifically mentioned stateless bean here, we'll come
to that later). Instead, the EJB client API just returns a
java.lang.reflect.Proxy instance of the remote view type that's being
looked up. This not just saves a network call, marshalling/unmarshalling
step but it also means that you can create an EJB proxy even when the
server isn't up yet. Later on, when the invocation on the proxy happens,
the EJB client API _does_ communicate with the server to carry out the
invocation.

[[is-the-lookup-optimization-applicable-for-all-bean-types]]
=== Is the lookup optimization applicable for all bean types?

In the previous section we (intentionally) mentioned that the lookup
optimization by the EJB client API project happens for stateless beans.
This kind of optimization is *not* possible for stateful beans because
in case of stateful beans, a lookup is expected to create a session for
that stateful bean and for session creation we do have to communicate
with the server since the server is responsible for creating that
session.

That's exactly why the EJB client API project expects the JNDI name
lookup string for stateful beans to include the " `?stateful`" string at
the end of the JNDI name:

[source, java]
----
context.lookup("ejb:myapp/myejbmodule//StatefulBean!org.myapp.ejb.Counter?stateful");
----

Notice the use of `"?stateful`" in that JNDI name. See
<<EJB_invocations_from_a_remote_client_using_JNDI,EJB invocations from a remote client using JNDI>> for
more details about such lookup.

The presence of " `?stateful`" in the JNDI name lookup string is a
directive to the EJB client API to let it know that a stateful bean is
being looked up and it's necessary to communicate with the server and
create a session during that lookup.

So as you can see, we have managed to optimize certain operations by
using the EJB client API for EJB lookup/invocation as against using the
remote-naming project. There are other EJB client API implementation
details (and probably more might be added) which are superior when it is
used for remote EJB invocations in client applications as against
remote-naming project which doesn't have the intelligence to carry out
such optimizations for EJB invocations. _That's why the remote-naming
project_ *_for remote EJB invocations_* _is considered "_ `deprecated`
_"_. Note that if you want to use remote-naming for looking up and
invoking on non-EJB remote objects then you are free to do so. In fact,
that's why that project has been provided. You can even use the
remote-naming project for EJB invocations (like we just saw), if you are
fine with _not_ wanting the optimizations that the EJB client API can do
for you or if you have other restrictions that force you to use that
project.

[[restrictions-for-ejbs]]
=== Restrictions for EJB's

If the remote-naming is used there are some restrictions as there is no
full support of the ejb-client features.

* No loadbalancing, if the URL conatains multiple "remote://" servers
there is no loadbalancing, the first available server will be used and
only in case it is not longer available there will be a failover to the
next available one.
* No cluster support. As a cluster needs to be defined in the
jboss-ejb-client.properties this feature can not be used and there is no
cluster node added
* No client side interceptor. The EJBContext.getCurrent() can not be
used and it is not possible to add a client interceptor
* No UserTransaction support
* All proxies become invalid if .close() for the related Initalcontext
is invoked, or the InitialContext is not longer referenced and gets
garbage-collected. In this case the underlying EJBContext is destroyed
and the conections are closed.
* It is not possible to use remote-naming if the client is an
application deployed on another JBoss instance
