ProcessEvent annotation

This is how the default implementation of the processEvent() method in GenricPortlet looks like, 

public void processEvent(EventRequest request, EventResponse response) throws PortletException, IOException {
    String eventName = request.getEvent().getQName().toString();
 try {
   // check for exact match
   Method eventMethod = processEventHandlingMethodsMap.get(eventName);
   if (eventMethod != null) {
  eventMethod.invoke(this, request, response);
  return;
   } else {
  // Search for the longest possible matching wildcard annotation
  int endPos = eventName.indexOf('}');
  int dotPos = eventName.lastIndexOf('.');
  while (dotPos > endPos) {
    String wildcardLookup = eventName.substring(0, dotPos + 1);
    eventMethod = processEventHandlingMethodsMap.get(wildcardLookup);
    if (eventMethod != null) {
   eventMethod.invoke(this, request, response);
   return;
    }
    if (dotPos == 0) {
   break;
    }
    dotPos = eventName.lastIndexOf('.', dotPos - 1);
  }
   }
 } catch (Exception e) {
   throw new PortletException(e);
 }
// if no event processing method was found just keep render params
response.setRenderParameters(request);
}


First it tries to figure out if there is a method with @ProcessEvent annotation, that matches current event, if yes it forwards control to that method if not it sets the current render parameters as new render parameters.

You can annotate a method use ProcessEvent annotation using two different approaches

  • Using QName: You can specify the fully qualified name of the event using "{" + Namespace URI + "}" + local part format. Ex. @ProcessEvent(qname="{http://wpcertification.blogspot.com}hello")

  • Using local Name:For using only the local part of the event name and leverage the default namespace defined in the portlet deployment descriptor with the default-namespace element the following alternative is provided: @ProcessEvent (name=), where the event name is only the local part.



You can download the sample portlet that i built to demonstrate how to use @ProcessEvent from here


package com.webspherenotes.portlet.jsr286;

import java.io.IOException;

import javax.portlet.Event;
import javax.portlet.EventRequest;
import javax.portlet.EventResponse;
import javax.portlet.GenericPortlet;
import javax.portlet.PortletException;
import javax.portlet.ProcessEvent;
import javax.portlet.RenderRequest;
import javax.portlet.RenderResponse;

import com.webspherenotes.portlet.events.Contact;

public class ProcessEventAnnotationPortlet extends GenericPortlet {

  protected void doView(RenderRequest request, RenderResponse response)
      throws PortletException, IOException {
    System.out.println("Entering ProcessActionAnnotationPortlet.doView()");
    response.setContentType("text/html");
    Contact contact = (Contact) request.getPortletSession().getAttribute(
        "contact");
    if (contact != null) {
      response.getWriter().println(
          "First Name " + contact.getFirstName() + "
 Last Name "
              + contact.getLastName() + "
 Email "
              + contact.getEmail());
    } else {
      response.getWriter().println("Contact not found in session ");
    }
    System.out.println("Exiting ProcessActionAnnotationPortlet.doView()");
  }

  //@ProcessEvent(name = "hello")
  @ProcessEvent(qname="{http://wpcertification.blogspot.com}hello")
  public void handleContactEvent(EventRequest request, EventResponse response)
      throws PortletException, IOException {
    System.out
        .println("Entering ProcessActionAnnotationPortlet.handleContactEvent()");
    Event event = request.getEvent();
    System.out.println("Event Name " + event.getName());
    System.out.println("Event Value " + event.getValue());
    Contact contact = (Contact) event.getValue();
    System.out.println("Contact First Name " + contact.getFirstName());
    System.out.println("Contact Last Name " + contact.getLastName());
    System.out.println("Contact Email " + contact.getEmail());
    request.getPortletSession().setAttribute("contact", contact);
    System.out
        .println("Entering ProcessActionAnnotationPortlet.handleContactEvent()");
  }

}


The ProcessEventAnnotationPortlet can act as target of hello event. It has a handleContactEvent method that can be used for handling the hello event. I can annotate it using either only local name like this @ProcessEvent(name = "hello") or using fully qualified name like this @ProcessEvent(qname="{http://wpcertification.blogspot.com}hello")

This is the portlet.xml for my Sample portlet

<?xml version="1.0" encoding="UTF-8"?>
<portlet-app xmlns="http://java.sun.com/xml/ns/portlet/portlet-app_2_0.xsd"
  version="2.0" 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">
  <portlet>
    <portlet-name>ProcessEventAnnotationPortlet</portlet-name>
    <display-name>Process Event Annotation Portlet</display-name>
    <portlet-class>com.webspherenotes.portlet.jsr286.ProcessEventAnnotationPortlet</portlet-class>
    <expiration-cache>0</expiration-cache>
    <supports>
      <mime-type>text/html</mime-type>
      <portlet-mode>view</portlet-mode>
      <portlet-mode>edit</portlet-mode>
    </supports>
    <portlet-info>
      <title>Process Event Annotation Portlet</title>
      <short-title>Process Event Annotation Portlet</short-title>
      <keywords>Process Event Annotation Portlet</keywords>
    </portlet-info>
    <supported-processing-event>
      <name>hello</name>
    </supported-processing-event>
  </portlet>
  <default-namespace>http://wpcertification.blogspot.com</default-namespace>
  <event-definition>
    <name>hello</name>
    <value-type>com.webspherenotes.portlet.events.Contact</value-type>
  </event-definition>
  
</portlet-app>

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