Documentation

The Portlet Plugin is used for developing JSR168 portlets using Struts 2.

portlet-class

To use the Struts 2 Portlet framework, use org.apache.struts2.portlet.dispatcher.Jsr168Dispatcher as the portlet class in your portlet.xml file:

<portlet-app
    version="1.0"
    xmlns="http://java.sun.com/xml/ns/portlet/portlet-app_1_0.xsd"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/portlet/portlet-app_1_0.xsd http://java.sun.com/xml/ns/portlet/portlet-app_1_0.xsd"
    id="my-portlet-app">

    <portlet id="MyPortlet">
        <description xml:lang="EN">My Portlet</description>
        <portlet-name>MyPortlet</portlet-name>
        <display-name xml:lang="EN">my-portlet</display-name>
    
        <portlet-class>org.apache.struts2.portlet.dispatcher.Jsr168Dispatcher</portlet-class>
        
        <!-- SNIP -->

    </portlet>
</portlet-app>

Portlet Init Parameters

Below is the init-param elements that you can set up in portlet.xml for configuring the portlet mode -> xwork namespace mappings for the portlet. Basically, you can think of the different portlet modes as different sub-applications, so it can be useful to set up the struts.xml configuration with different namespaces for the different portlets and modes:

e.g.

<init-param>
    <!-- Portlet namespace -->
    <name>portletNamespace</name>
    <value>/portletA</value>
</init-param>
<init-param>
    <!-- The base namespace of the view portlet mode -->
    <name>viewNamespace</name>
    <value>/view</value>
</init-param>
<init-param>
    <!-- The default action to invoke in view mode -->
    <name>defaultViewAction</name>
    <value>index</value>
</init-param>

This snippet from portlet.xml will set up the portlet with a namespace of /portletA/. This means that all requests to this portlet will get the namespace prepended when looking up the action. In addition, the _view portlet mode will map to the /view namespace, so a request for action myAction will resolve to the namespace and action /portletA/view/myAction. It also means that if no action is requested, the default action of index will be used for the request.

web.xml

If you want to access to expose the value stack through request attributes (e.g. if you want to use regular JSTL tags to access values in the stack), you have to configure the dispatcher servlet in your web application descriptor:

<servlet id="Struts2PortletDispatcherServlet">
    <servlet-name>Struts2PortletDispatcherServlet</servlet-name>
    <servlet-class>org.apache.struts2.portlet.dispatcher.DispatcherServlet</servlet-class>
</servlet>

If you're only using Struts 2 tags, configuring the dispatcher servlet is optional

Portlet Phases

The portlet specification describes that a portlet request cycle can consist of two phases, an event phase and a render phase. In case of an event in the portlet, it will always execute before the render phase. The event phase is typically for changing the state of the application. In a portlet, this is typically when a form is submitted. The render phase will then prepare and dispatch to the view. It's recommended that you set up the result from an action that is executed in the event phase to point to another action that is executed in the render phase, which again is responsible for dispatching to the actual view.

Portlet Result Dispatching

The struts-portlet-default package defines a special default Result Type, which is responsible for performing the result logic of an Action execution. Typically, this involves including a JSP for rendering, or preparing a render action if one is configured for the current event action.

This result type has three main modes of execution.

• If the Action is executed in the render phase, it will perform a PortletRequestDispatcher.include(req, res) to the resource specified in the location attribute.
• If the Action is executed in the event phase, and the result is an action mapping, it will set a render parameter on the ActionResponse to indicate which Action should be executed in the render phase. This follows good web application design, which promotes the use of a redirect after an event, which in this case means that an Action executed in the event phase will be followed by a redirect to an Action executed in the render phase.
• If the Action is executed in the event phase, and the result is not an action mapping, the result will prepare a special Action called "renderDirect" (specified in the struts-portlet-default package) whose sole purpose is to render the specified web resource (usually a JSP).

redirectAction

The action executed in event mode can pass render parameters to the next action to execute in render mode through parameters using the redirectAction result type:

<result type="redirectAction" name="success">
    <param name="actionName">displayCart</param>
    <param name="userId">${userId}</param>  
    <!-- If you want to redirect to a different portlet mode, use the portletMode parameter 
    <param name="portletMode">view</param>
    -->
</result>

This will set up a render parameter called userId with the value of the userId property on the value stack.

You can also use the portletMode parameter to change to a different portlet mode.

s:url and s:form tags

URLs in a portlet is handled quite different than for a regular web application. There's no such thing as "extension", there's simply an action name and a namespace, and they have to be specified using the respective tag attributes. URLs using the value attribute will be encoded as a resource URL and is only suitable for additional resources such as images and style sheets.

Example:

In addition, there are some additional tag attributes that are portlet specific. These are:

Typical usage for the portletUrlType is if you have a delete link that removes something from a database. To ensure this is done in the event phase, as recommended by the portlet specification (since it is a change of state), the url can use this attribute, e.g. <s:url action="deleteEntry" portletUrlType="action"/>

Other resources

Struts 2 Portlet Tutorial
JSR168 Specification