Portlet to Portlet Communication

Introduction #

The first version of the portlet specification, JSR-168/Portlet 1.0, did not include any support for Inter Portlet Communication. The second version, JSR-286/Portlet 2.0, has supported for IPC Mechanism.

JSR-286 makes it easy 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
    1. Public Render Parameters
    2. Event
    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

    <portlet>
        <private-session-attributes>false</private-session-attributes>
    </portlet>

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 ",PortletSession.APPLICATION_SCOPE);

2. Inter Portlet Communication (IPC) Mechanism #

2.1 Public-render-parameter Inter-portlet Communication #

 Illustration of IPC through public-render parameters

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=layout-set

Step 1: Add below attribute in "Sender-Portlet" #

    <portlet-app>
        <portlet>
            <supported-public-render-parameter>id1</supported-public-render-parameter>
        </portlet>
         
        <public-render-parameter>
            <identifier>id1</identifier>
            <qname xmlns:x="http://abc.com/userId">x:param1</qname>
        </public-render-parameter>
    </portlet-app>

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");

E.g.

    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-app>
        <portlet>
            <portlet-name >PortletB< /portlet-name>
            <supported-public-render-parameter>id1</supported-public-render-parameter>
        </portlet >
        <public-render-parameter>
            <identifier>id1</identifier>
            <qname xmlns:x="http://abc.com/userId">x:param1</qname>
        </public-render-parameter>
    </portlet-app>

Step 4 #

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 5 #

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

    response.removePublicRenderParameter("id1")

2.2 Event Inter-portlet Communication #

 Comic Illustration of IPC using Events

Portlet events that a portlet can receive and send.

In JSR-168 The only way to achieve eventing was through portlet session. The limitation of this approach was that the Portlets 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.properties, we can enable portlets to send and receive events from other portlets that are on different pages

    portlet.event.distribution=layout-set

Step 1: Sender Portlet #

portlet.xml

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

Add this inside <portlet> tag:

    <portlet-app>
        <portlet>
            <supported-publishing-event xmlns:x='http://liferay.com'>
                <qname>x:empinfo</qname>
            </supported-publishing-event>>
        </portlet>

        <event-definition xmlns:x='http://liferay.com'>
            <qname>x:empinfo</qname>
            <value-type>java.lang.String</value-type>
        </event-definition>
    </portlet-app>

Step 2: Set the event in process action #

    javax.xml.namespace.QName qName = new QName("http://liferay.com", "empinfo", "x");
    response.setEvent(qName, "Hi! You have received Event Data sent from Sender Portlet");

Step 3: Listener Portlet #

portlet.xml

    <portlet-app>

        <portlet>
            <supported-processing-event xmlns:x='http://liferay.com'>
                <qname>x:empinfo</qname>
            </supported-processing-event>
        </portlet>
        <event-definition xmlns:x='http://liferay.com'>
            <qname>x:empinfo</qname>
            <value-type>java.lang.String</value-type>
        </event-definition>
    </portlet-app>

Step 4: get the EVENT #

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

Lifecycle for IPC Event

 Lifecycle illustrated

    @javax.portlet.ProcessEvent(qname = "{http://liferay.com}empinfo")
    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("empInfo", value);
    }

2.3 Client-Side IPC #

There are 2 APIs for client side IPC.

Event generation (call from Portlet-A):

    Liferay.fire(
            '<eventName>', {
            name: value 
        }
    );

E.g.

    Liferay.fire(
            'planTravel', {
            origin: 'pune',
            destination : 'mumbai'
        }
    );

Event Listener (call from Portlet-B):

    Liferay.on(
            '<eventName>',
            function(event) {
                // your code
            }
    );

E.g.

    Liferay.on(
            '<eventName>',
            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 through Cookies.

But there are some limitations for cookies:

  1. It will not accept more than 4KB size of data
  2. 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:

    <script src="/html/js/jquery/cookie.js" type="text/javascript" > </script>
    
    function setCookie(docURL) {
        jQuery.cookie("cookieParam",docURL);
    }

To Set the Cookies through java/jsp:

    HttpServletResponse response = PortalUtil.getHttpServletResponse(actionResponse);
    Cookie cookieParam = new Cookie("cookieParam ", password);
    response.addCookie(cookieParam);

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 < cookies.length; i++) {
            if (cookies[i].getName().equals("cookieParam ")) {
                sessionid = cookies[i].getValue();
                break;
            }
        }
    }

- Gnaniyar Zubair rasikow@gmail.com

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Comments
Threaded Replies Author Date
Excellent Research Mr. ZUBAIR.... Thanks DarshanKumar N Bhatia November 30, 2010 2:58 AM
Thanks Darshan. Gnaniyar Zubair November 30, 2010 5:06 AM
Awesome one Zubair bhai... :-) Raja Seth May 24, 2013 12:22 AM
nice summary! Thank you, Gnaniyar Zubair. Jonas Yuan November 30, 2010 3:00 PM
thanks Jonas. Gnaniyar Zubair December 2, 2010 9:37 PM
nice post,thanks zubair Dhandapani S December 20, 2010 9:22 PM
Thanks dhandapani Gnaniyar Zubair December 21, 2010 6:58 AM
Nice post. But can you please explain how that... Sandeep Nair February 7, 2011 4:32 AM
Thanks Jonas shahrokh hassanzadegan February 12, 2011 5:24 AM
Hello Zubair Shouldn't be in the fire portlet... Alexandru Ionita March 30, 2011 10:32 AM
Hi, But if I open two instances of the same... Ravi Polepeddi November 15, 2011 4:49 AM
Thanks! Suraj Bihari November 15, 2011 1:36 PM
@Alexandru Ionita: yes.. should be... ugandhar @ November 28, 2011 1:36 AM
Really nice work! A lot of thanks! Alejandro Santamaría January 16, 2012 1:03 AM
Hello Zubair, Excellent Bro!! Thanks for... Ashish Renapurkar July 7, 2012 1:19 AM
Thanks for such a nice & concise tutorial. Prakash Khanchandani July 26, 2012 3:57 AM
thanks for solution Friends Team October 30, 2012 11:12 PM
Hi, I'm trying to use the Liferay javascript... Jeroen Koek December 31, 2012 2:49 AM
Sorry guys, I solved it myself. Due to the... Jeroen Koek December 31, 2012 3:33 AM
Nice work.. Karthikeyan M March 14, 2013 10:14 PM
awesome :) useful post mohammad azaruddin December 18, 2013 8:31 AM
Very well explained! +1 Pankaj Kathiriya June 18, 2014 5:26 AM

Excellent Research Mr. ZUBAIR....
Thanks
Posted on 11/30/10 2:58 AM.
Thanks Darshan.
Posted on 11/30/10 5:06 AM in reply to DarshanKumar N Bhatia.
nice summary! Thank you, Gnaniyar Zubair.
Posted on 11/30/10 3:00 PM.
thanks Jonas.
Posted on 12/2/10 9:37 PM in reply to Jonas X. Yuan.
nice post,thanks zubair
Posted on 12/20/10 9:22 PM.
Thanks dhandapani
Posted on 12/21/10 6:58 AM in reply to Dhandapani S.
Nice post. But can you please explain how that QName resolves namespace conflict in Public render parameter. In Eventing it is clear since we use qname to refer them in the lifecycle method. But in public render parameter we never make use of qname anywhere. We just use the identifier in Java as well as in supported public render parameter. How does qname actually resolve namespace issue for public render parameter?
Posted on 2/7/11 4:32 AM in reply to Gnaniyar Zubair.
Thanks Jonas
Posted on 2/12/11 5:24 AM.
Hello Zubair

Shouldn't be in the fire portlet the property <supported-publishing-event> instead of </supported-processing-event>. Otherwise you can't know which portlet is triggering and which portlet is listening.

regards
Posted on 3/30/11 10:32 AM.
Hi,

But if I open two instances of the same portlet in two browser tabs, how is one event different from the other ?
Posted on 11/15/11 4:49 AM in reply to Alexandru Ionita.
Posted on 11/15/11 1:36 PM.
@Alexandru Ionita: yes.. should be <supported-publishing-event> for Step 1: Sender Portlet
Posted on 11/28/11 1:36 AM in reply to Suraj Bihari.
Really nice work! A lot of thanks!
Posted on 1/16/12 1:03 AM in reply to Ugandhar Reddy.
Hello Zubair,

Excellent Bro!! Thanks for toooooooo informative article...

Regards n thanks ...
Ashish
Posted on 7/7/12 1:19 AM.
Thanks for such a nice & concise tutorial.
Posted on 7/26/12 3:57 AM in reply to Ashish Renapurkar.
thanks for solution
Posted on 10/30/12 11:12 PM in reply to Prakash Khanchandani.
Hi,
I'm trying to use the Liferay javascript api.
However this doesn't work when the user isn't logged on.
When I log on with a user the Liferay event bus is available but not when I'm not logged on.
Can you explain to me how I can enable this for the public (e.g. without a user logged on).
Thanks in advance.
Posted on 12/31/12 2:49 AM in reply to kumar g.
Sorry guys,
I solved it myself.

Due to the asynchronisation of the loading of the javascript some events where fired before I had registrated the Liveray.on.
To solve this you need to fire an event that is based on the PortletsAllReady event.

If that event arrives you can fire your own event to ensure that the listener is active to receive the events on load.

Hope this helps.
Posted on 12/31/12 3:33 AM in reply to J.P. Koek.
Posted on 3/14/13 10:14 PM.
Awesome one Zubair bhai... :-)
Posted on 5/24/13 12:22 AM in reply to DarshanKumar N Bhatia.
awesome emoticon useful post
Posted on 12/18/13 8:31 AM.
Very well explained! +1
Posted on 6/18/14 5:26 AM.