A PlugIn is a configuration wrapper for a module-specific resource or service that needs to be notified about application startup and application shutdown events (corresponding to when the container calls init and destroy on the corresponding ActionServlet instance). PlugIn objects can be configured in the struts-config.xml file, without the need to subclass ActionServlet simply to perform application lifecycle activities.

Implementations of this interface must supply a zero-argument constructor for use by ActionServlet . Configuration can be accomplished by providing standard JavaBeans property setter methods, which will all have been called before the init() method is invoked.

This interface can be applied to any class, including an Action subclass