Package org.camunda.bpm.application.impl

Class EjbProcessApplication

java.lang.Object
org.camunda.bpm.application.AbstractProcessApplication
org.camunda.bpm.application.impl.AbstractEjbProcessApplication
org.camunda.bpm.application.impl.EjbProcessApplication
All Implemented Interfaces:
ProcessApplicationInterface
Direct Known Subclasses:
DefaultEjbProcessApplication
public class EjbProcessApplication extends AbstractEjbProcessApplication

Common base class for writing EJB process applications.

An EJB Process Application exposes itself as a Session Bean Component inside the EJB container. This determines the invocation semantics when invoking code from the process application and the nature of the ProcessApplicationReference held by the process engine.

Usage

In order to add a custom EJB process application to your application, extend this class and configure it as follows:

 @ProcessApplication("my process application")
 @Singleton
 @Startup
 @ConcurrencyManagement(ConcurrencyManagementType.BEAN)
 @TransactionAttribute(TransactionAttributeType.REQUIRED)
 public class DefaultEjbProcessApplication extends EjbProcessApplication {

   @PostConstruct
   public void deploy() {
     super.deploy();
   }

   @PreDestroy
   public void undeploy() {
     super.undeploy();
   }
 }

(the same Metadata can of course be provided using an XML-based ejb-jar.xml deployment descriptor

Invocation Semantics

This allows the process engine as well as other applications to invoke this EJB Process Application and get EJB invocation semantics for the invocation. For example, if your process application provides a JavaDelegate implementation, the process engine will call the EjbProcessApplication's AbstractEjbProcessApplication.execute(java.util.concurrent.Callable) Method and from that method invoke the JavaDelegate. This makes sure that

  • the call is intercepted by the EJB container and "enters" the process application legally.
  • the JavaDelegate may take advantage of the EjbProcessApplication's invocation context and resolve resources from the component's Environment (such as a java:comp/BeanManager). 

                        Big pile of EJB interceptors
                                     |
                                     |  +--------------------+
                                     |  |Process Application |
                       invoke        v  |                    |
      ProcessEngine ----------------OOOOO--> Java Delegate   |
                                        |                    |
                                        |                    |
                                        +--------------------+

Process Application Reference

When the process application registers with a process engine (see ManagementService.registerProcessApplication(String, ProcessApplicationReference), the process application passes a reference to itself to the process engine. This reference allows the process engine to reference the process application. The EjbProcessApplication takes advantage of the Ejb Containers naming context and passes a reference containing the EJBProcessApplication's Component Name to the process engine. Whenever the process engine needs access to process application, the actual component instance is looked up and invoked.

Author:
Daniel Meyer