JSR 168 Portlet life cycle

Portlet life cycle

The basic portlet life cycle of a JSR 168 portlet is:

• Init: initialize the portlet and put the portlet into service
• Handle requests: process different kinds of action- and render-requests
• Destroy: put portlet out of service

The portlet container manages the portlet life cycle and calls the corresponding methods on the portlet interface.

Portlet interface

Every portlet must implement the portlet interface, or extend a class that implements the portlet interface. The portlet interface consists of the following methods:

• init(PortletConfig config): to initialize the portlet. This method is called only once after instantiating the portlet. This method can be used to create expensive objects/resources used by the portlet.
• processAction(ActionRequest request, ActionResponse response): to notify the portlet that the user has triggered an action on this portlet. Only one action per client request is triggered. In an action, a portlet can issue a redirect, change its portlet mode or window state, modify its persistent state, or set render parameters.
• render(RenderRequest request, RenderResponse response): to generate the markup. For each portlet on the current page, the render method is called, and the portlet can produce markup that may depend on the portlet mode or window state, render parameters, request attributes, persistent state, session data, or backend data.
• destroy(): to indicate to the portlet the life cycle's end. This method allows the portlet to free up resources and update any persistent data that belongs to this portlet.

Portlet modes

A portlet mode indicates the function a portlet performs. Usually, portlets execute different tasks and create different content depending on the functions they currently perform. A portlet mode advises the portlet what task it should perform and what content it should generate. When invoking a portlet, the portlet container provides the current portlet mode to the portlet. Portlets can programmatically change their mode when processing an action request.

JSR 168 splits portlet modes into three categories:

1. Required modes: Every portal must support the modes Edit, Help, and View. A portlet must at least support the View mode used to render markup for a page. The Edit mode is used to change per-user settings to customize the portlet markup, and the Help mode is used to show a help screen.
2. Optional custom modes: These are modes that a portal may support; while in an optional mode, a portlet might not be called. The optional modes include the About mode to display an "about" message; the Config mode to let administrators configure the portlet; Edit_defaults mode to let an administrator preset the Edit mode's values; the Preview mode to show the portlet's preview; and the Print mode to render a view that can easily print.
3. Portal vendor-specific modes: These modes are not defined in the specification and are therefore vendor specific.

Window states

A window state indicates the amount of portal page space that will be assigned to the content generated by a portlet. When invoking a portlet, the portlet container provides the current window state to the portlet. The portlet may use the window state to decide how much information it should render. Portlets can programmatically change their window state when processing an action request.

JSR 168 defines the following window states:

• Normal: Indicates that a portlet may share the page with other portlets. This is the default window state.
• Maximized: Indicates that a portlet may be the only portlet on the portal page or that the portlet has more space compared to other portlets in the portal page, and can therefore produce richer content than in a normal window state.
• Minimized: Indicates that the portlet should only render minimal output or no output at all.