Accessing the local session bean

An EJB client application accesses the appropriate local session bean through the home interface of the bean.

Why and when to perform this task

The session bean can be either the LocalBusinessFlowManager session bean for process applications or the LocalHumanTaskManager session bean for human task applications.

Steps for this task

  1. Add a reference to the local session bean to the application deployment descriptor. Add the reference to one of the following files:
    • The application-client.xml file, for a Java™ 2 Platform, Enterprise Edition (J2EE) client application
    • The web.xml file, for a Web application
    • The ejb-jar.xml file, for an Enterprise JavaBeans™ (EJB) application
    The reference to the local home interface for process applications is shown in the following example:
    <ejb-local-ref>
    	<ejb-ref-name>ejb/LocalBusinessFlowManagerHome</ejb-ref-name>
    	<ejb-ref-type>Session</ejb-ref-type>
    	<local-home>com.ibm.bpe.api.LocalBusinessFlowManagerHome</local-home>
    	<local>com.ibm.bpe.api.LocalBusinessFlowManager</local>
    </ejb-local-ref>
    The reference to the local home interface for task applications is shown in the following example:
    <ejb-local-ref>
    	<ejb-ref-name>ejb/LocalHumanTaskManagerHome</ejb-ref-name>
    	<ejb-ref-type>Session</ejb-ref-type>
    	<local-home>com.ibm.task.api.LocalHumanTaskManagerHome</local-home>
    	<local>com.ibm.task.api.LocalHumanTaskManager</local>
    </ejb-local-ref>

    If you use WebSphere® Integration Developer to add the EJB reference to the deployment descriptor, the binding for the EJB reference is automatically created when the application is deployed. For more information on adding EJB references, refer to the WebSphere Integration Developer documentation.

  2. Retrieve a reference to the local home interface of the local session bean from Java Naming and Directory Interface (JNDI).

    The following example shows this step for a process application:

    // Obtain the default initial JNDI context
    InitialContext initialContext = new InitialContext();
    
      // Lookup the local home interface of the LocalBusinessFlowManager bean
     
       LocalBusinessFlowManagerHome processHome = 
            (LocalBusinessFlowManagerHome)initialContext.lookup
            ("java:comp/env/ejb/LocalBusinessFlowManagerHome");
    The home interface of the local session bean contains a create method for EJB objects. The method returns the local interface of the session bean.
  3. Access the local interface of the local session bean.

    The following example shows this step for a process application:

    LocalBusinessFlowManager process = processHome.create();

    Access to the session bean does not guarantee that the caller can perform all of the actions provided by the bean; the caller must also be authorized for these actions. When an instance of the session bean is created, a context is associated with the instance of the session bean. The context contains the caller's principal ID, group membership list, and indicates whether the caller has one of the Business Process Choreographer J2EE roles. The context is used to check the caller's authorization for each call, even when global security is not set. If global security is not set, the caller's principal ID has the value UNAUTHENTICATED.

  4. Call the business functions exposed by the service interface.

    The following example shows this step for a process application:

    process.initiate("MyProcessModel",input);
    Calls from applications are run as transactions. A transaction is established and ended in one of the following ways:
    • Automatically by WebSphere Application Server (the deployment descriptor specifies TX_REQUIRED).
    • Explicitly by the application. You can bundle application calls into one transaction:
      // Obtain user transaction interface
      UserTransaction transaction= 
             (UserTransaction)initialContext.lookup("jta/usertransaction");
      
      // Begin a transaction
      transaction.begin();
      
      // Applications calls ...
      
      // On successful return, commit the transaction
      transaction.commit();
    Tip: To prevent database deadlocks, avoid running statements similar to the following in parallel transactions:
    // Obtain user transaction interface
    UserTransaction transaction= 
           (UserTransaction)initialContext.lookup("jta/usertransaction");
    
    transaction.begin();
    
    //read lock on the activity instance 
    process.getActivityInstance(aiid);     
    //write lock on the activity instance
    process.claim(aiid);               
         
    transaction.commit();

Example

Example

Here is an example of how steps 2 through 4 might look for a task application.

//Obtain the default initial JNDI context
InitialContext initialContext = new InitialContext();

//Lookup the local home interface of the LocalHumanTaskManager bean
LocalHumanTaskManagerHome taskHome = 
        (LocalHumanTaskManagerHome)initialContext.lookup
        ("java:comp/env/ejb/LocalHumanTaskManagerHome");

...
//Access the local interface of the local session bean
LocalHumanTaskManager task = taskHome.create();

...
//Call the business functions exposed by the service interface
task.callTask(tkiid,input);
Related concepts
Authorization roles for business processes
Authorization roles for human tasks

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