Sunday, November 28, 2010

Portlet to Portlet Communication


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.

There are 3 ways to share the data between 2 portlets.

1. Portlet session

2. IPC Mechanisms

2.1 Public Render Parameters

2.2 Event

2.3 Client-Side IPC

3. Cookies

1.Portlet Session

By default , Each war has its own session and will not be shared with other wars. Liferay provides a mechanism by which Portlets can share session attributes across WARs.

A PortletSession is created for each user per portlet application. This makes the PortletSession useful for communicating all user related information among different portlets in the same portal application.

Step 1: set below attributes in Portlet1

liferay-portlet.xml :




Step 2: To set the Session:

PortletSession session = renderRequest.getPortletSession();

session.setAttribute("sessionValue",some-value , PortletSession.APPLICATION_SCOPE);

Step 3 : Get the Session Value in Portlet2

PortletSession ps = renderRequest.getPortletSession();

String tabNames = (String)ps.getAttribute("sessionValue ",ps.APPLICATION_SCOPE);


2. IPC Mechanism

2.1 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:


Step 1: Add below attribute in “Sender-Portlet”








<qname xmlns:x="">x:param1



Note: We can declare a list of public paramters for a portlet application.

Step 2:

We can set render parameter in the processAction() method by using the defined public render parameter identifier as the key.

response.setRenderParameter("id1", “someIdValue”);


public void processAction(ActionRequest request, ActionResponse response)

throws IOException, PortletException { ........

response.setRenderParameter("id1", “someIdValue”); ........


Step 3 : Receiver Portlet Portlet “portlet.xml”

Specify the render parameter the portlet would like to share in the

portlet section.

< portlet >

< portlet-name >PortletB< /portlet-name >

<supported-public-render-parameter >id1< /supported-public-render-parameter >

< /portlet >






Step 4 :

A portlet can read public render parameter using following method



Public render parameters are merged with regular parameters so can also be read using


Step 5:

A portlet can remove a public render parameter by invoking following methods.



Event : IPC ( Inter Portlet Communication) Mechanisms :

Portlet events that a portlet can receive and send.

In JSR-168 :
The only way to achive eventing was through portlet session.
Limitation : Portlet has to be in the same web application.

In JSR-286 :
JSR 286 (Portlet 2.0) defines a lifecycle for events, so that eventing is possible between portlets that are in different web applications.

By adding the following property in portal-ext, we can enable portlets to send and receive events from other portlets that are on different pages


Step 1: Sender Portlet



The portlet standard defines a way of telling the portlet container which portlet is responsible for sending an event.



<supported-processing-event xmlns:x=''>




<event-definition xmlns:x=''>





Step 3 : Set the event in process action:

javax.xml.namespace.QName qName =

new QName("", "empinfo", "x");



"Hai You have received Event Data sent from Sender Portlet");

Step 4: Listner Portlet





<supported-processing-event xmlns:x=''>




<event-definition xmlns:x=''>





Step 5: get the EVENT:

This Even will be called after processAction as shown in the picture:

Lifecycle for IPC Event:

@javax.portlet.ProcessEvent(qname = "{}empinfo")

public void handleProcessempinfoEvent(

javax.portlet.EventRequest request, javax.portlet.EventResponse response)

throws javax.portlet.PortletException, {

javax.portlet.Event event = request.getEvent();

String value = (String) event.getValue();

System.out.print("value in process event>>>>>>>>>" + value);

response.setRenderParameter("empInfo", value);



2.3 Client-Side IPC :

There are 2 APIs for client side IPC.

Event generation (call from portlet A):'', {
name : value

e.g.'planTravel', {
origin : 'pune',
destination : 'mumbai'

Event Listener ((call from portlet B):

Liferay.on('', function(event) {


Liferay.on('planTravel', function(event) {
showNews('', event.origin);
showNews('', event.destination);



3. Cookies

Other than the IPC mechanism, There is an easiest way to get the data between portlets on different pages called COOKIES.

But there are some limitations for cookies that it will not accept more than 4KB size datas and the biggest limitation is, the 20 cookies per server limit, and so it is not a good idea to use a different cookie for each variable that has to be saved

Portlet 1 :

To Set the Cookies through jQuery :

function setCookie(docURL) {



To Set the Cookies through java / jsp:

HttpServletResponse response = PortalUtil.getHttpServletResponse(


Cookie cookieParam = new Cookie("cookieParam ", password);


Portlet 2:

To get the Cookies through jQuery :

jQuery.cookie("cookieParam ");

To get the Cookie through java/ jsp :

String sessionid = "";

Cookie[] cookies = request.getCookies();

if (cookies != null) {

for (int i = 0; i <>

if (cookies[i].getName().equals("cookieParam ")) {

sessionid = cookies[i].getValue();





Gnaniyar Zubair


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