Developing Applications with WebLogic Server

Programming Application Lifecycle Events

The following sections describe how to create applications that respond to WebLogic Server application lifecycle events:

Understanding Application Lifecycle Events

Application lifecycle listener events provide handles on which developers can control behavior during deployment, undeployment, and redeployment. This section discusses how you can use the application lifecycle listener events.

Four application lifecycle events are provided with WebLogic Server, which can be used to extend listener, shutdown, and startup classes. These include:

Registering Events in weblogic-application.xml

In order to use these events, you must register them in the weblogic-application.xml deployment descriptor. See Application Deployment Descriptor Elements. Define the following elements:

Programming Basic Lifecycle Listener Functionality

You create a listener by extending the abstract class (provided with WebLogic Server) weblogic.application.ApplicationLifecycleListener. The container then searches for your listener.

You override the following methods provided in the WebLogic Server ApplicationLifecycleListener abstract class to extend your application and add any required functionality:

Listing 9-1 illustrates how you override the ApplicationLifecycleListener. In this example, the public class MyListener extends ApplicationLifecycleListener.

import weblogic.application.ApplicationLifecycleListener;

import weblogic.application.ApplicationLifecycleEvent;

public class MyListener extends ApplicationLifecycleListener {

  public void preStart(ApplicationLifecycleEvent evt) {

     System.out.println

     ("MyListener(preStart) -- we should always see you..");

   } // preStart

  public void postStart(ApplicationLifecycleEvent evt) {

     System.out.println

     ("MyListener(postStart) -- we should always see you..");

   } // postStart

  public void preStop(ApplicationLifecycleEvent evt) {

     System.out.println

     ("MyListener(preStop) -- we should always see you..");

   } // preStop

  public void postStop(ApplicationLifecycleEvent evt) {

     System.out.println

     ("MyListener(postStop) -- we should always see you..");

   } // postStop

   public static void main(String[] args) {

     System.out.println

     ("MyListener(main): in main .. we should never see you..");

   } // main

}

Listing 9-2 illustrates how you implement the shutdown class. The shutdown class is attachable to preStop and postStop events. In this example, the public class MyShutdown does not extend ApplicationLifecycleListener because a shutdown class declared in the weblogic-application.xml deployment descriptor does not need to depend on any WebLogic Server-specific interfaces.

import weblogic.application.ApplicationLifecycleListener;

import weblogic.application.ApplicationLifecycleEvent;

public class MyShutdown {

   public static void main(String[] args) {

     System.out.println

     ("MyShutdown(main): in main .. should be for post-stop");

   } // main

}

Listing 9-3 illustrates how you implement the startup class. The startup class is attachable to preStart and postStart events. In this example, the public class MyStartup does not extend ApplicationLifecycleListener because a startup class declared in the weblogic-application.xml deployment descriptor does not need to depend on any WebLogic Server-specific interfaces.

import weblogic.application.ApplicationLifecycleListener;

import weblogic.application.ApplicationLifecycleEvent;

public class MyStartup {

   public static void main(String[] args) {

     System.out.println

     ("MyStartup(main): in main .. should be for pre-start");

   } // main

}

Examples of Configuring Lifecycle Events with and without the URI Parameter

The following examples illustrate how you configure application lifecycle events in the weblogic-application.xml deployment descriptor file. The URI parameter is not required. You can place classes anywhere in the application $CLASSPATH. However, you must ensure that the class locations are defined in the $CLASSPATH. You can place listeners in APP-INF/classes or APP-INF/lib, if these directories are present in the EAR. In this case, they are automatically included in the $CLASSPATH.

The following example illustrates how you configure application lifecycle events using the URI parameter. In this case, the archive foo.jar contains the classes and exists at the top level of the EAR file. For example: myEar/foo.jar

  <listener>

       <listener-class>MyListener</listener-class>

       <listener-uri>foo.jar</listener-uri>

  </listener>

  <startup>

       <startup-class>MyStartup</startup-class>

       <startup-uri>foo.jar</startup-uri>

  </startup>

  <shutdown>

       <shutdown-class>MyShutdown</shutdown-class>

       <shutdown-uri>foo.jar</shutdown-uri>

  </shutdown>

The following example illustrates how you configure application lifecycle events without using the URI parameter.

 <listener>

       <listener-class>MyListener</listener-class>

  </listener>

  <startup>

       <startup-class>MyStartup</startup-class>

  </startup>

  <shutdown>

       <shutdown-class>MyShutdown</shutdown-class>

  </shutdown>

Understanding Application Lifecycle Event Behavior During Re-deployment

Application lifecycle events are only triggered if a full re-deployment of the application occurs. During a full re-deployment of the application—provided the application lifecycle events have been registered—the application lifecycle first commences the shutdown sequence, next re-initializes its classes, and then performs the startup sequence.

For example, if your listener is registered for the full application lifecycle set of events (preStart, postStart, preStop, postStop), during a full re-deployment, you see the following sequence of events:

Programming Application Version Lifecycle Events

The following sections describe how to create applications that respond to WebLogic Server application version lifecycle events:

Understanding Application Version Lifecycle Event Behavior

WebLogic Server provides application version lifecycle event notifications by allowing you to extend the ApplicationVersionLifecycleListener class and specify a lifecycle listener in weblogic-application.xml. See Application Deployment Descriptor Elements and Examples of Configuring Lifecycle Events with and without the URI Parameter.

Application version lifecycle events are invoked:

Types of Application Version Lifecycle Events

Four application version lifecycle events are provided with WebLogic Server:

Example of Production Deployment Sequence When using Application Version Lifecycle Events

The following table provides an example of a deployment (V1), production redeployment (V2), and an undeploy (V2).