Service POJOS

Service POJOs allow you to define POJOs as JBoss services. The way you define them is very similar to how you define stateless or stateful session beans. One very important difference is that there will only ever be ONE instance of the service bean. i.e. it is not pooled - the bean instance is a singleton. The singleton bean contains shared state, so data set by one client is accessible by other clients.

Example simple ServicePOJO

ServiceOne also implements ServiceOneManagement.java. ServiceOne.java has been annotated with @Management. JBoss will inspect this interface, and create and install an MBean implementing the attributes and operations defined in the @Management interface. The MBean will work on the same singleton bean instance as the remote and local interfaces.

The default ObjectName used for a service bean is

   jboss.j2ee:jar=<jar file>,service=EJB3,name=<Name of @Service bean>,type=<interface>

   jboss.j2ee:jar=tutorial.jar,service=EJB3,name=ServiceOne,type=ManagementInterface

Lifecycle

• Lifecycle methods
• Dependencies

Lifecycle methods

   void create() throws Exception;
   void start() throws Exception;
   void stop();
   void destroy();

You do not need to create all these methods, you can pick and choose. If present the service container will call these methods as follows:

• create() - called by the server when the service is created and all the services it depends upon have been created too. At this point the service (and all the services it depends on) is installed in the JMX server, but is not yet fully functional.
• start() - called by the server when the service is started and all the services it depends upon have been started too. At this point the service (and all the services it depends on) is fully functional.
• stop() - called by the server when the service is stopped. At this point the service (and all the services that depend on it) is no longer fully operational.
• destroy() - called by the server when the service is destroyed and removed from the MBean server. At this point all the MBeans that depend on the

Depends and custom JMX object name

   @Service (objectName="tutorial:service=serviceTwo")
   @Depends ("jboss.j2ee:jar=tutorial.jar,service=EJB3,name=ServiceOne,type=service,type=ManagementInterface")
   public class ServiceTwo implements ServiceTwoManagement
   {
      ...
   }

The @Depends annotation specifies that this service depends on the service created for ServiceOne. i.e. it cannot be started until the service created for ServiceOne has been started. The definition of the @Depends annotation type is:

   public @interface Depends
   {
      String[] value();
   }

In other words, you could specify an array of object names if you depended on more than one service.

Rather than installing a service under its default object name, you can specify a custom name in the @Service annotation. ServiceTwo will get bound under tutorial:service=serviceTwo instead of the default which would have been jboss.j2ee:jar=tutorial.jar,service=EJB3,name=ServiceTwo,type=ManagementInterface.

Depends injection

   @Depends ("jboss.j2ee:jar=tutorial.jar,name=ServiceOne,service=EJB3,type=ManagementInterface")
   public ObjectName serviceOneName;
   
   @Depends ("tutorial:service=serviceTwo")
   public void setServiceTwo(ServiceTwoManagement service2)
   {
      this.service2 = service2;
   }

The object name of ServiceOne gets injected into the serviceOneName field. More interesting is the injection of ServiceTwo. setServiceTwo() takes a parameter, which is the ServiceTwoManagement management interface of ServiceTwo. The server creates a dynamic proxy for the ServiceTwoManagement interface, and injects that. This means that you can call the methods on the service2 field without caring that you are actually invoking methods on another service.

Interceptors

   @AroundInvoke
   public Object intercept(InvocationContext ctx) throws Exception
   {
      System.out.println("ServiceThree - Interceptor");
      return ctx.proceed();
   }

Building

Unix:    $ export JBOSS_HOME=<where your jboss 4.0 distribution is>
Windows: $ set JBOSS_HOME=<where your jboss 4.0 distribution is>
$ ant

In the JBoss console you should see output similar to this when the .jar archive is deployed

16:52:30,326 INFO  [Ejb3Module] found EJB3 service bean: org.jboss.tutorial.service.bean.ServiceOne
16:52:30,387 INFO  [Ejb3Module] found EJB3 service bean: org.jboss.tutorial.service.bean.ServiceThree
16:52:30,397 INFO  [Ejb3Module] found EJB3 service bean: org.jboss.tutorial.service.bean.ServiceTwo
16:52:30,427 INFO  [ProxyDeployer] no declared remote bindings
16:52:30,437 INFO  [ProxyDeployer] there is remote interfaces
16:52:30,437 INFO  [ProxyDeployer] default remote binding has jndiName of org.jboss.tutorial.service.bean.ServiceOneRemote
16:52:35,113 INFO  [STDOUT] ServiceOne - Creating
16:52:35,113 INFO  [STDOUT] ServiceOne - Starting
16:52:35,244 INFO  [ProxyDeployer] no declared remote bindings
16:52:35,945 INFO  [STDOUT] ServiceTwo - Starting
16:52:35,965 INFO  [ProxyDeployer] no declared remote bindings
16:52:36,585 INFO  [STDOUT] ServiceThree - Starting
16:52:36,585 INFO  [EJB3Deployer] Deployed: file:/C:/cygwin/home/Kab/cvs/jboss-head/build/output/jboss-5.0.0alpha/server/all/deploy/tutorial.jar

ServiceOne starts before ServiceTwo which starts before ServiceThree, due to the dependencies we set up earlier.

Then to run the example

$ ant run
Buildfile: build.xml

run:
     [java] attribute value for singleton obtained via JMX is what we set via remote i/f: 100
     [java] Hello from service One
     [java] Hello from service Two

The JBoss console should show the following output

17:05:07,796 INFO  [STDOUT] ServiceThree - Interceptor
17:05:07,796 INFO  [STDOUT] ServiceThree - Calling ServiceOne.sayHello() via JMX server
17:05:07,806 INFO  [STDOUT] ServiceThree - Interceptor
17:05:07,806 INFO  [STDOUT] ServiceThree - Calling ServiceTwo.sayHello() via MBean proxy