Developing Lifecycle Listeners

12 Developing Lifecycle Listeners

Lifecycle listener modules provide a means of running short or long duration Java-based tasks within the Oracle GlassFish Server environment, such as instantiation of singletons or RMI servers. These modules are automatically initiated at server startup and are notified at various phases of the server life cycle.

Note	Lifecycle listener modules are deprecated. Support for them is included for backward compatibility. Implementing the org.glassfish.api.Startup interface instead is recommended.

All lifecycle module classes and interfaces are in the as-install`/modules/``glassfish-api.jar` file.

For Javadoc tool pages relevant to lifecycle modules, see the com.sun.appserv.server package.

The following topics are addressed here:

Server Life Cycle Events
The LifecycleListener Interface
The LifecycleEvent Class
The Server Lifecycle Event Context
Deploying a Lifecycle Module
Considerations for Lifecycle Modules

Server Life Cycle Events

A lifecycle module listens for and performs its tasks in response to the following events in the server life cycle:

After the INIT_EVENT, the server reads the configuration, initializes built-in subsystems (such as security and logging services), and creates the containers.
After the STARTUP_EVENT, the server loads and initializes deployed applications.
After the READY_EVENT, the server is ready to service requests.
After the SHUTDOWN_EVENT, the server destroys loaded applications and stops.
After the TERMINATION_EVENT, the server closes the containers, the built-in subsystems, and the server runtime environment.

These events are defined in the LifecycleEvent class.

The lifecycle modules that listen for these events implement the LifecycleListener interface.

The LifecycleListener Interface

To create a lifecycle module is to configure a customized class that implements the com.sun.appserv.server.LifecycleListener interface. You can create and simultaneously execute multiple lifecycle modules.

The LifecycleListener interface defines this method:

public void handleEvent(com.sun.appserv.server.LifecycleEvent event)
throws ServerLifecycleException

This method responds to a lifecycle event and throws a com.sun.appserv.server.ServerLifecycleException if an error occurs.

A sample implementation of the LifecycleListener interface is the LifecycleListenerImpl.java file, which you can use for testing lifecycle events.

The `LifecycleEvent` Class

The com.sun.appserv.server.LifecycleEvent class defines a server life cycle event. The following methods are associated with the event:

public java.lang.Object.getData()
This method returns an instance of java.util.Properties that contains the properties defined for the lifecycle module.
public int getEventType()
This method returns the type of the last event, which is INIT_EVENT, STARTUP_EVENT, READY_EVENT, SHUTDOWN_EVENT, or TERMINATION_EVENT.
public com.sun.appserv.server.LifecycleEventContext.getLifecycleEventContext()
This method returns the lifecycle event context, described next.

A LifecycleEvent instance is passed to the LifecycleListener.handleEvent method.

The Server Lifecycle Event Context

The com.sun.appserv.server.LifecycleEventContext interface exposes runtime information about the server. The lifecycle event context is created when the LifecycleEvent class is instantiated at server initialization. The LifecycleEventContext interface defines these methods:

public java.lang.String[].getCmdLineArgs()
This method returns the server startup command-line arguments.
public java.lang.String.getInstallRoot()
This method returns the server installation root directory.
public java.lang.String.getInstanceName()
This method returns the server instance name.
public javax.naming.InitialContext.getInitialContext()
This method returns the initial JNDI naming context. The naming environment for lifecycle modules is installed after the STARTUP_EVENT. A lifecycle module can look up any resource by its jndi-name attribute after the READY_EVENT.

If a lifecycle module needs to look up resources, it can do so after the READY_EVENT. It can use the getInitialContext method to get the initial context to which all the resources are bound.

Deploying a Lifecycle Module

For instructions on how to deploy a lifecycle module, see the GlassFish Server Open Source Edition Application Deployment Guide, or see the asadmin create-lifecycle-module command in the GlassFish Server Open Source Edition Reference Manual.

You do not need to specify a classpath for the lifecycle module if you place it in the domain-dir`/lib` or domain-dir`/lib/classes` directory for the Domain Administration Server. Do not place it in the lib directory for a particular instance, or it will be deleted when that instance synchronizes with the Domain Administration Server.

Considerations for Lifecycle Modules

The resources allocated at initialization or startup should be freed at shutdown or termination. The lifecycle module classes are called synchronously from the main server thread, therefore it is important to ensure that these classes don’t block the server. Lifecycle modules can create threads if appropriate, but these threads must be stopped in the shutdown and termination phases.

The LifeCycleModule class loader is the parent class loader for lifecycle modules. Each lifecycle module’s classpath is used to construct its class loader. All the support classes needed by a lifecycle module must be available to the LifeCycleModule class loader or its parent, the Connector class loader.

You must ensure that the server.policy file is appropriately set up, or a lifecycle module trying to perform a System.exec() might cause a security access violation. For details, see The server.policy File.

The configured properties for a lifecycle module are passed as properties after the INIT_EVENT. The JNDI naming context is not available before the STARTUP_EVENT. If a lifecycle module requires the naming context, it can get this after the STARTUP_EVENT, READY_EVENT, or SHUTDOWN_EVENT.