Simple Generic Portlet example with Liferay

Portlets are the fragments of a portal application. A Portlet contains different lifecycle stages: init, render, processAction, processEvent, serveResource, destroy. The JSR-168/JSR-286 Portlet specification standards specify these life cycle stages of a simple generic portlet.

Before continuing, take a look at this article to learn how to create a Liferay portlet using the LDS IDE.

We have used Liferay version 6.2 with the Apache Tomcat server version 7 on this article.

Portlet modes
Creating a generic portlet
Conclusion

Portlet modes

A portlet can have different modes like VIEW, EDIT, HELP.

VIEW: View mode is to render the content to the users.
EDIT: Edit mode helps the user edit manage the configurations, and customize the behavior of the portlet.
HELP: Help mode should provide helpful information about the portlet.

The Following are the methods javax.portlet.Portlet class contains to support above mentioned portlet modes:

init(): This method initializes the portlet.
doView(): This method performs required actions before rendering the page for portlet in VIEW mode.
doEdit()/ doHelp(): These methods are handler methods for portlets that are in EDIT/HELP mode.
processAction(): To handle actions.
serveResource(): The method that handles the AJAX calls.
processEvent(): This method handles the portlet events.
public void destroy(): Removal of a portlet from a page invokes this lifecycle method.

Creating a generic portlet

A portlet that is extending Generic portlet must override the doView() method. Below is the simple Generic Liferay portlet example with VIEW mode.

By default Liferay portlet supports the VIEW mode.

Create a Liferay project. Create a new action class and extend GenericPortlet.
Change the parameter value of the “<portlet-class>” tag in the portlet.xml file to the newly created action class.
Implement the doView() method. We are setting the value of the renderRequest parameter “name” and including the view.jsp page to render the result.
The init() is the method used to initialize the portlet. We are getting the “view-template” value from the portlet.xml configuration file and setting it into a variable called “viewJsp” that renders the JSP page for VIEW mode.
The “include()” method is a convenient method invoked just before the application renders the portlet page.
We are retrieving requestDispatcher from portletContext. We also made sure that portletContext is not null before retrieving the request dispatcher.
Liferay, by default, comes with Apache’s “common logging” classes. We also need to add a few imports to enable the logging.

Below is the complete portlet class SamplePortlet.java.

package com.genportlet;
import com.liferay.portal.kernel.exception.SystemException;
import com.liferay.portal.kernel.log.LogFactoryUtil;
import java.io.IOException;
import javax.portlet.GenericPortlet;
import javax.portlet.PortletException;
import javax.portlet.PortletRequestDispatcher;
import javax.portlet.RenderRequest;
import javax.portlet.RenderResponse;
import com.liferay.portal.kernel.log.Log;
public class SamplePortlet extends GenericPortlet {
  public void init() {
     viewJsp = getInitParameter("view-template");
  }
  protected void doView(RenderRequest renderRequest, RenderResponse renderResponse) throws PortletException, IOException
  {
     String name = "ABC";
     renderRequest.setAttribute("name", name);
     try {
        include(viewJsp, renderRequest, renderResponse);
     } 
    catch (SystemException e) {
      e.printStackTrace();
     }
  }
 public void include(String jsp, RenderRequest renderRequest, 
              RenderResponse renderResponse) throws SystemException, 
IOException {
     PortletRequestDispatcher prd = getPortletContext().getRequestDispatcher(jsp);
     if(prd == null) {
        _log.error("Error in adding path..!!");
     }
     else {
       try {
         prd.include(renderRequest, renderResponse);
       } 
       catch (PortletException e) {
         e.printStackTrace();
       }
     }
  }
   protected String viewJsp;
   private static Log _log = LogFactoryUtil.getLog(SamplePortlet.class);
}

Add the following code to view.jsp page to retrieve the parameter called “name” and display the parameter value.

The “<portlet:definedObjects/>” tag gives access to objects like RenderRequest, RenderResponse, PortletConfig, etc.

view.jsp:

<%@page import="com.liferay.portal.kernel.util.ParamUtil"%>
<%@ taglib uri="http://java.sun.com/portlet_2_0" prefix="portlet" %>
<portlet:defineObjects />
This is the <b>Test</b> portlet in View mode.
<%String param = ParamUtil.get(request, "name", "");%>
<h1>Hello <%=param%>!!!</h1>

Now deploy the portlet and add it to a page. Below is the result:

Conclusion

In this article, we learned how to create a simple generic portlet.

We also learned about different portlet modes and created a simple generic Liferay portlet.

We also learned how to set attributes and retrieve them in the JSP file.

Simple Generic Portlet example with Liferay

Table of Contents

Portlet modes

Creating a generic portlet

Conclusion

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