JSR286 : Public Render Parameter

When the Java Portlet Specification( draft was released last year, i had written a blog on Public Render Parameter feature. Recently the proposed final draft was released, it has some changes in public render parameter feature. In this blog i will explain the feature with an example.

In JSR 168, the render parameters set in processAction is only available in the render of the same portlet.

With the Public Render Parameters feature, the render parameters set in the processAction of one portlet will be available in render of other portlets also. Using public render parameters instead of events avoids the additional process event call.

In order to allow coordination of render parameters with other portlets, within the same portlet application or across portlet applications, the portlet can declare public render parameters in its deployment descriptor using the public-render-parameter element in the portlet application section. Public render parameters can be viewed and changed by other portlets or components.

In the portlet section each portlet can specify the public render parameters it would like to share via the supported-public-render-parameter element. The supported-public-render-parameter element must reference the identifier of a public render parameter defined in the portlet application section in a public-render-parameter element.

In the code, the portlets should use the defined public render parameter identifier to access the public render parameter(new addition in the proposed final draft).

To create portlets that use the public render parameters, follow these steps

1. Declare the render parameters to be shared in the portlet.xml file by setting the public render parameters at the portlet application level.


<portlet-app xmlns="http://java.sun.com/xml/ns/portlet/portlet-app_2_0.xsd"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/portlet/portlet-app_2_0.xsd
http://java.sun.com/xml/ns/portlet/portlet-app_2_0.xsd"
id="myPortletApp" version="2.0">
<portlet>
. . .
</portlet>

<public-render-parameter>
<identifier>zip-id</identifier>
<qname xmlns:x="http://sun.com/params">x:zip</qname>
</public-render-parameter>

</portlet-app>

2. Specify the render parameter that the portlet would like to share in the portlet section.

<portlet-app xmlns="http://java.sun.com/xml/ns/portlet/portlet-app_2_0.xsd"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/portlet/portlet-app_2_0.xsd
http://java.sun.com/xml/ns/portlet/portlet-app_2_0.xsd"
id="myPortletApp" version="2.0">
<portlet>
<description>WeatherPortlet</description>
<portlet-name>WeatherPortlet</portlet-name>
<display-name>WeatherPortlet</display-name>
<portlet-class>com.sun.portal.portlet.WeatherPortlet</portlet-class>
......
<supported-public-render-parameter>zip-id</supported-public-
render-parameter>
</portlet>

<portlet>
<description>MapPortlet</description>
<portlet-name>MapPortlet</portlet-name>
<display-name>MapPortlet</display-name>
<portlet-class>com.sun.portal.portlet.MapPortlet</portlet-class>
. . .
<supported-public-render-parameter>zip-id</supported-public-
render-parameter>
</portlet>
. . .
</portlet-app>



3. Set the render parameter in the processAction() method:

public class WeatherPortlet extends GenericPortlet {
. . .
public void processAction(ActionRequest req, ActionResponse res)
throws IOException, PortletException {
. . .
res.setRenderParameter("zip-id", zip);
}
. . .
}

Sample Application

You can download the binary WeatherMap.war file to deploy and run the sample application in . You can also get the source for the sample. If you are behind a firewall you need need to set the proxy in the webcontainer configuration.

The figure shows the Weather and Map portlets. The Weather portlet sets the zip-id which is declared as a Public Render Parameter. This parameter is supported by both Weather and Map portlets. Any change in the value of zip by Weather portlet is reflected during the render phase of both weather and map portlets.