When the Java Portlet Specification(JSR 286)
early draft was released last year, i had written a blog on the Eventing. Recently the proposed final draft was
released, it has some changes in the eventing feature. In
this blog i will explain the feature with an example.
To create portlets that use the eventing feature, follow these steps(snippets from EventingMap sample application):
1.Declare the events in the portlet.xml
1.1 Set the event definition at the portlet application level. This specifies the event name and the object type.
Note: The object must be serializable and must be instrumented with valid JAXB annotation
<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>
<event-definition>
<qname xmlns:x="http:sun.com/mapevents">x:Continent</qname>
<value-type>com.sun.portal.portlet.mapevent.Continent</value-type>
</event-definition>
</portlet-app>
@XmlRootElement
public class Continent implements Serializable {
public Continent() {
}
private String name;
private String description;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDescription() {
return description;
}
public void setDescription(String description)
this.description = description;
}
}
1.2 In the portlet section, specify the event name defined above for those portlets that want to publish this event.
<portlet>
<description>ContinentPortlet</description>
<portlet-name>ContinentPortlet</portlet-name>
.................
<supported-publishing-event>
<qname xmlns:x="http:sun.com/events">x:Continent</qname>
</supported-publishing-event>
</portlet>
1.3 In the portlet section, specify the event name defined above for those portlets that want to process this event.
<portlet>
<description>ContinentMapPortlet</description>
<portlet-name>ContinentMapPortlet</portlet-name>
. . .
<supported-processing-event>
<qname xmlns:x="http:sun.com/events">x:Continent</qname>
</supported-processing-event>
</portlet>
<portlet>
<description>ContinentInfoPortlet</description>
<portlet-name>ContinentInfoPortlet</portlet-name>
. . .
<supported-processing-event>
<qname xmlns:x="http:sun.com/events">x:Continent</qname>
</supported-processing-event>
</portlet>
. . .
</portlet-app>
2. Issue an event in the portlet that was specified as supported-publishing-event in the portlet.
public class ContinentPortlet extends GenericPortlet {
public void processAction(ActionRequest request, ActionResponse response)
throws PortletException,IOException {
QName qname = new QName("http:sun.com/mapevents" , "Continent")
String value = request.getParameter("continent");
Continent continent = new Continent();
continent.setName(value);
ResourceBundle rb = getPortletConfig().getResourceBundle(request.getLocale());
continent.setDescription(rb.getString(value));
response.setEvent(qname, continent);
}
. . .
}3. Process the event in the portlet that has specified as supported-processing-event in the portlet
public class ContinentInfoPortlet extends GenericPortlet {
public void processEvent(EventRequest request, EventResponse response) {
Event event = request.getEvent();
if(event.getName().equals("Continent")){
Continent payload = (Continent)event.getValue();
response.setRenderParameter("continentDescription",
payload.getDescription());
}
}
. . .
}
public class ContinentMapPortlet extends GenericPortlet {
public void processEvent(EventRequest request, EventResponse response) {
Event event = request.getEvent();
if(event.getName().equals("Continent")){
Continent payload = (Continent)event.getValue();
response.setRenderParameter("continentName", payload.getName());
}
}
. . .
}
You can download the binary
file EventingMap.war to deploy and run the sample application in OpenPortal Portlet Container 2.0 Beta2(or latest). You can also get the source for the sample.
The figure shows the World Map, Continent Information, and Continent Map
Portlets that participate in the event. Clicking on any continent in
the World Map triggers an event. This event is processed by the
Continent Information and Continent Map Portlets to show the relevant
information.
