Portlet Lifecycle

A portlet is managed through a well defined life cycle that defines how it is loaded, instantiated and initialized, how it handles requests from clients, and how it is taken out of service. This life cycle of a portlet is expressed through the init, render, processAction, and destroy methods of the Portlet interface.

Method signature: init(PortletConfig config) render(RenderRequest request, RenderResponse response) processAction(ActionRequest request, ActionResponse response) processEvent(EventRequest request, EventResponse response) serveResource(ResourceRequest request, ResourceResponse response) destroy()

The init(PortletConfig config) is called once, immediately after a new portlet instance is created. It can be used to perform startup tasks and is akin to a servlets init method. PortletConfig represents read-only configuration data, specified in a portlet's descriptor file, portlet.xml(more on this file later). For example, PortletConfig provides access to initialization parameters. The render(RenderRequest request, RenderResponse response) method follows processAction in the chain of lifecycle methods. Render generates the markup that will be made accessible to the portal user. RenderRequest and RenderResponse methods, also subinterfaces of PortletRequest and PortletResponse, are available during the rendering of a portlet. The way in which the render method generates output may depend on the portlet's current state. The processAction(ActionRequest request, ActionResponse response) method is called in response to a user action such as clicking a hyperlink or submitting a form. In this method, a portlet may invoke business logic components, such as JavaBeans, to accomplish its goal. The ActionRequest and ActionResponse Interfaces are subinterfaces of PortletRequest and PortalRequest. In processAction, a portlet may modify its own state as well as persistent information about a portlet. In addition to this your portlet can decide to implement EventPortlet interface which says that portlet can be target of event (Target of inter portlet communication). The EventPortlet interface defines processEvent(EventRequest request, EventResponse response) method that you should override to implement the logic that should be executed when portlet receives event. This is useful if you want to use inter portlet communication If your portlet wants to support Ajax access then you can also implement ResourceServingPortlet interface, that defines serveResource(ResourceRequest request, ResourceResponse response) method. Once you define this method you can create a resource URL from your portlet using resourceURL tag and make request to the URL to get the fragment of portlet. This helps you avoid creating a Servlet in same application as that of the portelt just to support Ajax The destroy() method is the last lifecycle method, called just before a portlet is garbage collected and provides a last chance to free up portlet resources.