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You could have some custom initialization and cleanup when an application, a session, a desktop or an execution is instantiated or about to being destroyed.

There are two steps:

  1. Implements the corresponding interface. For example, WebAppInit for application's initialization
  2. Register it in WEB-INF/zk.xml, or in Java.

Interfaces

Task Interface
Application Init WebAppInit
Application Cleanup WebAppCleanup
Session Init SessionInit
Session Cleanup SessionCleanup
Desktop Init DesktopInit
Desktop Cleanup DesktopCleanup
Execution Init ExecutionInit
Execution Cleanup ExecutionCleanup

Notice that ZK will instantiate an object from the class you registered for each callback. For example, an object is instantiated to invoke DesktopInit.init(Desktop, Object), and another object instantiated to invoke DesktopCleanup.cleanup(Desktop), even if you register a class that implements both DesktopInit and DesktopCleanup.

If you have something that is initialized in the init callback and have to clean it up in the cleanup callback, you cannot store it as a data member. Rather, you have to maintain it by yourself, such as storing it in the desktop's attributes (Desktop.setAttribute(String, Object)), session's attributes or application's attributes.

Registration

The registration in WEB-INF/zk.xml is the same, no matter what interface you implement:

<listener>
    <listener-class>my.MyImplementation</listener-class>
</listener>

The registration in Java is done by Configuration.addListener(Class).

webapp.getConfiguration().addListener(my.MyImplementation.class);

Version History

Last Update : 2010/12/2


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Copyright © Potix Corporation. This article is licensed under GNU Free Documentation License.



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