The first version of the portlet specification, JSR-168/portlet1.0, did not include any support for Inter Portlet Communication. The second version, JSR-286/ portlet2.0, which is supported for IPC Mechanism.
IPC is made easy with JSR-286 to share the data between two portlets. Using IPC mechanisms, we can share the data from ACTION to VIEW phase and VIEW-VIEW Phase.

Public Render Parameter : IPC ( Inter Portlet Communication) :

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.
By adding the following property in portlet-ext, we can enable portlets to share render states with other portlets that are on different pages: portlet.public.render.parameter.distribution=ALL_PORTLETS

Follow Steps to create IPC Portlet in Liferay 6.1.1 ga2

Step 1: Create new demoipc-portlet

Give first portlet name:sender

Step 2: Create second portlet in same project

Give portlet name:receiver

Step 3: In package com.test make two java class file

Sender.java

 
package com.test;
import java.io.IOException;
import java.util.Random;
import javax.portlet.ActionRequest;
import javax.portlet.ActionResponse;
import javax.portlet.PortletException;
import javax.portlet.PortletRequestDispatcher;
import javax.portlet.ProcessAction;
import javax.portlet.RenderRequest;
import javax.portlet.RenderResponse;
import javax.xml.namespace.QName;
import com.liferay.portal.kernel.log.Log;
import com.liferay.portal.kernel.log.LogFactoryUtil;
import com.liferay.util.bridges.mvc.MVCPortlet;
 
 
/**
 * Portlet implementation class sender
 */
public class sender extends MVCPortlet {
  @ProcessAction(name="pitchBall")
public void pitchBall(ActionRequest request, ActionResponse response) {
 
String pitchType = null;
System.out.println("pitch call");
// Send an Event that the ball has been pitched.
Random random = new Random(System.currentTimeMillis());
int pitch = random.nextInt(3) + 1;
 
switch (pitch) {
case 1:
pitchType = "Fast Ball";
break;
case 2:
pitchType = "Curve Ball";
break;
case 3:
pitchType = "Slider";
break;
// should never print
default:
pitchType = "Screw Ball";
}
 
 
pitchType=pitchType+"Hai You have received Event Data sent from Sender Portlet";
 
javax.xml.namespace.QName qName =
new QName("http://liferay.com", "ipc.pitch", "x");
response.setEvent(
qName,
pitchType);
System.out.println("call here");
 
}
}

Receiver.java

 
  package com.test;
import javax.portlet.Event;
import javax.portlet.EventRequest;
import javax.portlet.EventResponse;
import javax.portlet.ProcessEvent;
import com.liferay.util.bridges.mvc.MVCPortlet;
/**
 * Portlet implementation class receiver
 */
public class receiver extends MVCPortlet {
@javax.portlet.ProcessEvent(qname = "{http://liferay.com}ipc.pitch")
public void handleProcessempinfoEvent(
javax.portlet.EventRequest request, javax.portlet.EventResponse
response)
throws javax.portlet.PortletException, java.io.IOException { 
javax.portlet.Event event = request.getEvent();
String value = (String) event.getValue();
System.out.print("value in process event>>>>>>>>>" + value);
response.setRenderParameter("ipc.pitch", value);
}
 
}
 
Step 4: Edit the portlet.xml
 
-Add below attribute in “Sender-Portlet”
-Before closing of </portlet>
 
<supported-processing-event xmlns:x='http://liferay.com'>
<qname>x:ipc.pitch</qname>
</supported-processing-event>
 
 
 
</portlet>
<event-definition xmlns:x='http://liferay.com'>
<qname>x:ipc.pitch</qname>
<value-type>java.lang.String</value-type>
</event-definition>
 
</portlet-app>
 
Note: We can declare a list of public paramters for a portlet application.
-Add below attribute in “recevier-Portlet”
 
-Before closing of </portlet>
<supported-processing-event xmlns:x='http://liferay.com'>
<qname>x:ipc.pitch</qname>
</supported-processing-event>
 
 
 
</portlet>
<event-definition xmlns:x='http://liferay.com'>
<qname>x:ipc.pitch</qname>
<value-type>java.lang.String</value-type>
</event-definition>
 
</portlet-app>

In my example I have created both portlet in same project so here I have add both changes in same portlet.xml file

Portlet.xml

 
 
 
  <?xml version="1.0"?>
 
<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" version="2.0">
 
<portlet>
<portlet-name>sender</portlet-name>
<display-name>sender</display-name>
<portlet-class>com.test.sender</portlet-class>
<init-param>
<name>view-jsp</name>
<value>/html/sender/view.jsp</value>
</init-param>
<expiration-cache>0</expiration-cache>
<supports>
<mime-type>text/html</mime-type>
<portlet-mode>view</portlet-mode>
</supports>
<portlet-info>
<title>sender</title>
<short-title>sender</short-title>
<keywords></keywords>
</portlet-info>
<security-role-ref>
<role-name>administrator</role-name>
</security-role-ref>
<security-role-ref>
<role-name>guest</role-name>
</security-role-ref>
<security-role-ref>
<role-name>power-user</role-name>
</security-role-ref>
<security-role-ref>
<role-name>user</role-name>
</security-role-ref>
<supported-processing-event xmlns:x='http://liferay.com'>
<qname>x:ipc.pitch</qname>
</supported-processing-event>
 
</portlet>
<portlet>
<portlet-name>receiver</portlet-name>
<display-name>receiver</display-name>
<portlet-class>com.test.receiver</portlet-class>
<init-param>
<name>view-jsp</name>
<value>/html/receiver/view.jsp</value>
</init-param>
<expiration-cache>0</expiration-cache>
<supports>
<mime-type>text/html</mime-type>
<portlet-mode>view</portlet-mode>
</supports>
<portlet-info>
<title>receiver</title>
<short-title>receiver</short-title>
<keywords></keywords>
</portlet-info>
<security-role-ref>
<role-name>administrator</role-name>
</security-role-ref>
<security-role-ref>
<role-name>guest</role-name>
</security-role-ref>
<security-role-ref>
<role-name>power-user</role-name>
</security-role-ref>
<security-role-ref>
<role-name>user</role-name>
</security-role-ref>
<supported-processing-event xmlns:x='http://liferay.com'>
<qname>x:ipc.pitch</qname>
</supported-processing-event>
</portlet>
<event-definition xmlns:x='http://liferay.com'>
<qname>x:ipc.pitch</qname>
<value-type>java.lang.String</value-type>
</event-definition>
 
</portlet-app>

Step 5: A portlet can read public render parameter using following method

request.getPublicParameterMap()
Note: Public render parameters are merged with regular parameters so can also be
read using
request.getParameter(“id1”);

Step 6: A portlet can remove a public render parameter by invoking following methods

response.removePublicRenderParameter(“id1”)

Step 7: Make view.jsp for sender and receiver

 
 
  Make view.jsp in  html/sender/view.jsp
View.jsp
<%@ taglib uri="http://java.sun.com/portlet" prefix="portlet" %>
 
<portlet:defineObjects />
vbjhbnj
<p>Click the link below to pitch the ball. </p>
<a href="<portlet:actionURL name="pitchBall"></portlet:actionURL>">Pitch!</a>
 
 
Make view.jsp in  html/recevier/view.jsp
View.jsp
<%@ taglib uri="http://java.sun.com/portlet" prefix="portlet" %>
 
<portlet:defineObjects />
 
 
<%
String pitch = (String)renderRequest.getParameter("ipc.pitch");
%>
<p>And the pitch is....</p>
<p>
<% if (pitch!=null) { %>
<%=pitch %>!
<% } else { %>
... waiting for pitch.
<% } %>