Develop applications that use the Asynchronous Invocation API on Liberty

We can use the Asynchronous Invocation API to transfer events that require processing in the context of a Session Initiation Protocol (SIP) application session to any server in a cluster based on the related application session ID. The Asynchronous Invocation API transfers the event task to the correct server. Read the API documentation for information on the following asynchronous work classes:

• com.ibm.websphere.sip.AsynchronousWork
• com.ibm.websphere.sip.AsynchronousWorkListener

For more information about the API classes, see Program interfaces.

When running code outside of a SIP thread, application developers can use the Asynchronous Invocation API to create an object. They can then configure the server to run that object either on a different thread in the same container, or on a different server, if that is where the session exists. The following example shows the class structure for the AsynchronousWork class, which is the abstract base class that is extended when we use the API.

	public abstract class AsynchronousWork implements Serializable
	{ 	private String sessionId;
	public AsynchronousWork(String sessionId)
	{ 	this.sessionId = sessionId;
	....
	}
	public void dispatch (AsynchronousWorkListener listener)
	{ 	....
	}
	public abstract Serializable doAsyncTask();
	}

1. Extend the abstract class AsynchronousWork with the SIP-related code. The extended implementation of the doAsyncTask() method is invoked on the target server containing the SipApplicationSession, and whose ID was set in the constructor that implements the AsynchronousWork class. The implementation class must pass the session ID to the base class by calling super in the constructor.

   public class MyClass extends AsynchronousWork
   { String _sessionId;
   
   public MyClass(String sessionId) { super(sessionId);
   _sessionId = sessionId;
   }
   
   // This code is invoked on the target machine or thread
   public Serializable doAsyncTask() { // Application code goes here; for instance:
   appSession = sessionUtils.getApplicationSession(_sessionId);
   appSession.createRequest().....
   
   Serializable myResponse = new MyResponse();
   myResponse.setStatus(200);
   return (myResponse);
   }
   }

2. To receive information about the task completion, implement the AsynchronousWorkListener class, as in the following example. The code in these methods is invoked on the source server.

   public class MyListener implements AsynchronousWorkListener
   { public void workCompleted(Serializeable myResponse)
   { ....
   }
   public void workFailed(int reasonCode, String reason)
   { }
   }
   

3. Invoke the asynchronous call; for example, when we receive the proprietary message, use this sample code as an example.

   public void onMyMessage()
   { // Obtain the session ID from the message or
   // somewhere else
   String sessionId = obtainIdFromMessage();
   
   // Create the runnable
   MyClass myClass = new MyClass(sessionId);
   
   // Create the listener
   MyListener myListener = new MyListener();
   
   // Dispatch it
   myClass.dispatch(myListener);
   }