Portlet Introduction / Portlet Technology Introduction

Portlet is small fragment of dynamic content in the web page. And this dynamic content may be text,HTML,xml or some other MIME format. Portlet technology implemented by JSR 168 and JSR 286 standards.

Generally in web application we are very familiar with servlet technology and portlet technology is similar to servlet technology but it consist its own features. servlet technology based on client and server architecture in the web world here the client is browser.

Portlets life cycle is managed by portlet containers these are in application servers. portlet life cycle consist different stages like instantiation,serving and destroying. Portlet containers are similar to servlet containers to manage entire life cycle of portlet.

Generally in the portlet technology each page consist one or more portlets and each portlet render dynamic content to make complete web page.

In technical understand portlet technology implemented in Java in the package javax.portlet.

This portlet API consist many interfaces and implementation classes to developed portlet based application in the web world.

How does portlets are differed from servlet

Generally in servlet web application each servlet will be referred by URL to invoke or access and each web page content will be served by one servlet but in portlets each page will be served by different portlet and each portlet will have its own lifecycle and own URL pattern to execute.

Servlet will generate dynamic content which send to browser and it’s in single web page but portlet will server fragment of dynamic content and portal page is responsible to aggregate content from different portlet to generate whole page.

There are many people implemented the portlet technology.

Liferay

JetSpeed

Pluto

uPortal

WebLogic

Websphere

Entando

Understanding the Portlet Technology

Basically we need to following things to run portlet based application

JRE

Portlet Container+Application Server

Portlets

Portlet Container

Portlet containers is responsible for run the portlet and it provides the required run time environment. Portlet containers manage the life cycle of portlets. When ever portal server send the request then portlet containers receive the requests and its invoke the respective portlet to process request means its instantiated the portlet and execute appropriate life cycle methods to prepare response. Portlet container send portlet response back to portal server like that portal server receive responses of different portlets and aggregate all response to complete client request.

Application Server

Application servers are responsible to process client request and send response back to client. Application server provided different services to manage and run web applications. The services like JMS, JNDI, JTS, JAAS, JDO,Connection Pooling and all these services required by the applications.

Application servers integrated with different containers to provide different run time environments like servlet containers to provides run time environment to execute servlets, portlet containers is to provides the run time environment to execute portlet, EJB containers to provided environment to execute Enterprise Java Beans applications.

Apart from this application severs have more capabilities to provide different services to run different technology based applications.

Portlets

As we already know each portlet has it own life cycle and which will be managed by portlet container. According to the JSR 168 standard portlet have three life cycle stages.

Basic portlet consist following life cycle stages

Portlet life cycle  

init:

Initialize the portlet and put the portlet into service

Handle requests:

Process different kinds of action- and render-requests

Destroy:

Put portlet out of service

Theoretically we have 3 life cycle stages in portlets and these will be implemented via portlet interface. Portlet interface is implemented in javax.portlet package by Sun Microsystems.

Every portlet that should implements the portlet interface or it should extend the class that already implemented the portlet interface.

As we know portlet have three life cycle staged and the following are interface methods which handle portlet life cycle in portlet implementation.

init(PortletConfig config):

This method is initialize the portlet and this will be called only once when portlet is instantiated, we can say when we drag and drop portlet in page.

If any necessary functionality required at initial time of portlet we will use this method and write code here. It is similar to servlet init method. This method can be used to create expensive objects/resources used by the portlet.

processAction(ActionRequest request, ActionResponse response):

When user is requested to server then portlet will execute process action method.

This method will notify the portlet that used has triggered an action this portlet. , a portlet can issue a redirect, change its portlet mode or window state, modify its persistent state, or set render parameters.

render(RenderRequest request, RenderResponse response):

Render method will generate content and that will be send to web client.

In the portal page we have many portlet we have triggered action in one portlet then all portlet will be executed render method to aggregate dynamic content. The portlet can produce markup that may depend on the portlet mode or window state, render parameters, request attributes, persistent state, session data, or backend data.

destroy ():

Indicate to the portlet the life cycle's end. This method allows the portlet to free up resources and update any persistent data that belongs to this portlet.

Note:

In the portlet life cycle for each action or request the final method is render method. Render method will be called for every time to aggregate content or produce content.

Generally portlet have different URL to call these methods like Action URL and Render URL. 

 

Action URL will execute portlet porcessAction(----) method and then it will be execute the render(----) method.

Render URL will execute the portlet render (---) method only. 

Portlet Lyfecycle Execution Process 

Portlet Characteristics

Portlet have addition Characteristics when we compare with servlet.

Portlet Widow States:

Portlet has different window states. Window state specifies how portlet will look in the page .Window state decides how much space will be accommodated in portlet page.

The following are important window states as for JSR 168 Standards.

Maximized:

When portlet state is decided as Maximized then entire page only one portlet is visible.

Generally we will use this state after perform some action then we will make widow state is Maximized.

Normal:

Specified that is portlet may share the page with other portlets. This is the default window state.

Minimized:

Portlet should only render minimal output or no output at all.

Portlet Modes:

Portlet mode specifies that the function will be performed by portlet.

Generally following are the portlet modes that each portlet should support as for JSR 168&286 standards.

View:

This view mode is when portlet is access or render then portlet is in view mode and this is default mode for portlet.

Edit:

Edit mode will be used to edit some portlet functionality and generally we wil use this mode for administrator to modify or edit something.

Help:

This will used to provide content to end user about portlet i.e how to use and access portlet like help information. 

 

Persistent storage for preferences:

Portlets provide a Portlet Preferences object for storing user preferences. These preferences are stored in a persistent data store, so they will be available across server restarts. As a developer, you don't have to worry about the actual implementation of how it is stored.

Portlet Sessions:

Like Http Session in the portlet technology also have different scopes of session to share data among the portlet or with in the portlet. Portlet also can use Http Session.

Portlet Session by default scope is portlet level what ever the data stored in Portlet Session can be available with in portlet. If we want share data among the portlets then we have to use application level scope so that data can be shares across the portlets.

Portlet technology have concept called publics render parameters to exchange data among portlets this is we can all it as Inter Portlet Communication.

We can use portlet sessions or public render parameters to establish communication among portlets which are in same page.

Portal context 

Portal context provides information such as the portal vendor, the portal version, and specific portal properties. The information allows the portlet to use specific vendor extensions when being called by a portal that supports these extensions and, when being called by other portals, to return to some simpler default behavior.

Properties 

Properties communicate vendor-specific settings between the portlet and portlet container, and between the portlet and the portal. 

These properties show up in several places in JSR 168. The portlet can read String properties with getProperty() from: 

ActionRequest, to receive properties that are action-request specific

RenderRequest, to receive properties that are render-request specific

PortalContext, to receive properties that are portal specific and do not change for different requests 

The portlet can write String properties with setProperty() to: 

ActionResponse, to set properties in response to an action request

RenderResponse, to set properties in response to a render request

Packaging and deployment

Portlet are packages as web archive file(WAR) this archive file consist of portlet deployment descriptors, resources and other java libraries which are required by portlets.

In the portlet application we have two deployment descriptors that is web.xml and portlet.xml

web.xml specifies the things related to web application deployment properties

portlet.xml specifies the portlet application related deployment properties and it always describes only one specific portlet application.

portlet application deployment is a two-step deployment that deploys the Web application into the application server and the portlets into the portal server.

Author

Meera Prince
Liferay Certified Professional Developer 

Liferay Top Contributor Award Winner(2013,2014)

http://www.liferaysavvy.com

Read More

Liferay MVC Portlet Form Submission

Introduction:

Generally when we work with Portlet Application development we need to submit form and display the data in JPS page or we need to store the data into database.

In this article I only explain simply submit the form data to portlet action methods and then display submitted data in JSP pages.

In web application we will use Html form to post or pass the data to server side. We have another way to send the data to server is as request parameters in URL. In general Form is the way to take user inputs and send to the server side.

Note:

In the URL request if we send any data then it will be always a simple string values.

Forms also submitted the data as URL query string, this we can observe when we use GET method in forms.

Before Start this article Please have a look into following article

LiferayMVC Portlet Development with Liferay IDE

Well we are aware of Liferay MVC Portlet Development.

Environment:

Liferay IDE 2.x+Eclipse (Kepler) +Liferay Plugins SDK 6.2+Tomcat 7.x Liferay Portal Bundle

Steps:

1. Create Simple MVC Portlet Using Liferay IDE
2. Define HTML Form in JSP page
3. Capture Form Data in Portlet Class Action Method
4. Display Submitted Data in other JSP Page.

Create Simple MVC Portlet Using Liferay IDE

In the first steps we need to create Liferay MVC Portlet with help of Liferay IDE.

Follow the article and create Simple Liferay MVC Portlet.

LiferayMVC Portlet Development with Liferay IDE

Define HTML Form in JSP page

Once we done above step then we will create simple html form in JSP page and we will use different form elements to send the data to server.

We have following form elements to send data to server/portlet action method

input text , input radio , input check box, text area , input file and select box Note: We will use different form elements for different purpose Example: Single selection we will use Radio Multiple selected options we will use check box or multi select box For text input we will use text fields, If more text then we will use text area Send file then we will use file input element

Example Html Form in JSP page

<%@ taglib uri="http://java.sun.com/portlet_2_0" prefix="portlet" %> <portlet:defineObjects /> <portlet:actionURL var="addStudentActionURL" windowState="normal" name="addStudent"> </portlet:actionURL> <h1>Student Form</h1> <form action="<%=addStudentActionURL%>" name="studentForm"  method="POST"> <b>First Name</b><br/> <input  type="text" name="<portlet:namespace/>firstName" id="<portlet:namespace/>firstName"/><br/> <b>Last Name</b><br/> <input type="text" name="<portlet:namespace/>lastName" id="<portlet:namespace/>lastName"/><br/> <b>Exam Fee</b><br/> <input type="text" name="<portlet:namespace/>examFee" id="<portlet:namespace/>examFee"/><br/> <b>Gender</b><br/> <input type="radio" name="<portlet:namespace/>sex" value="male">Male<br> <input type="radio" name="<portlet:namespace/>sex" value="female">Female<br/> <b>Subjects Obtained</b><br/> <input type="checkbox" name="<portlet:namespace/>subjects" value="Maths">Maths<br> <input type="checkbox" name="<portlet:namespace/>subjects" value="Physics">Physics<br> <input type="checkbox" name="<portlet:namespace/>subjects" value="Chemistry">Chemistry<br> <input type="checkbox" name="<portlet:namespace/>subjects" value="Bio Technology">Biotechnology<br> <input type="checkbox" name="<portlet:namespace/>subjects" value="Computer Science">Computer Science<br> <b>Academic Year</b><br> <select name="<portlet:namespace/>acadamicYear">   <option value="I Year">I Year</option>   <option value="II Year">II Year</option>   <option value="III Year">III Year</option>   <option value="IV Year">IV Year</option> </select><br> <b>Address</b><br/> <textarea rows="4" cols="50" name="<portlet:namespace/>address"> </textarea><br/> <input type="submit" name="addStudent" id="addStudent" value="Add Student"/> </form>

Note:

We should append <portlet:namespace/> to each input “name” attribute  then only portlet action class consider it in request parameter otherwise it will be ignored by portlet action class.

 This behavior we can observe from Liferay 6.2 version. I already explained regarding to this in previous articles.

In the form “action” attribute we need to give action URL so that form input data will be available in respective action method.

We should specify the “method” attribute to form then only form will be submitted to respective portlet action method.

Capture form Data in Portlet Class Action Method

We will get form input data or request parameter values in the following ways.

request.getParamter(“inputName/requestParameterName”)

We will use above method so that we can get values in portlet class action method

Example:

Form Input Element <input  type="text" name="<portlet:namespace/>firstName" id="<portlet:namespace/>firstName"/><br/> Get the value in Action Method String firstName=actionRequest.getParameter("firstName");

Note:

We already know all request parameter values and form input values always string values when it reaches action method or server side. Based on our expected type we need to type cast the string values.

If we use above method we need to type cast values when we want specific data type.

ParamUtil Class

Liferay have given ParamUtil class which consists of many methods and we will use those methods to capture request parameter values or form input values.

Example:

Form Input Element <input  type="text" name="<portlet:namespace/>firstName" id="<portlet:namespace/>firstName"/><br/> Get the value in Action Method String firstName=ParamUtil.getString(actionRequest,"firstName");

This class has different methods so that we can directly get expected data type without type cast the values

Example:

If our expected Data type is double

Form Input Element <input type="text" name="<portlet:namespace/>examFee" id="<portlet:namespace/>examFee"/> Get the value in Action Method double examFee=ParamUtil.getDouble(actionRequest,"examFee");

Similarly we have different data type returning methods so that it is very convenient way to get the data as we expected data type.

Example Available Methods:

Access Multiple Values

Some time user may select multiple options or we can say user may check multiple check boxes.

ParamUtil have method i.e. ParamUtil.getParameterValues(---) it will capture array of string values for specific form input element and generally it is checkboxes with same “name” attribute or multiple option selected combo box.

Syntax:

ParamUtil.getParameterValues(actionRequest,"inputName",defaultValue);

Scenario:

Assume scenario Student may obtained multiple subjects

Form Input Check Box Element <b>Subjects Obtained</b><br/> <input type="checkbox" name="<portlet:namespace/>subjects" value="Maths">Maths<br> <input type="checkbox" name="<portlet:namespace/>subjects" value="Physics">Physics<br> <input type="checkbox" name="<portlet:namespace/>subjects" value="Chemistry">Chemistry<br> <input type="checkbox" name="<portlet:namespace/>subjects" value="Bio Technology">Biotechnology<br> <input type="checkbox" name="<portlet:namespace/>subjects" value="Computer Science">Computer Science<br> Get the Multiple values for Single Input in Action Method String[] subjects = ParamUtil.getParameterValues(actionRequest,"subjects",null);

Note:

When we observe check box names are same for everyone and this is called same element “name” attribute carrying multiple values.

Display Submitted Data in other JSP Page.

We already aware of form submitted to Portlet Action Method and we capture d the data in the above steps. Now we will send captured form data to JSP page from portlet class action method.

We will use set Attribute method to pass data from Action Method to JSP page.

Before send data to JSP page first we need to prepare data as some specific objet format so that we can pass object through set Attribute method

Scenario:

We already get the all student data through form submission and now we will use map object to prepare all student details.

Example:

In Action Method

String firstName=ParamUtil.getString(actionRequest,"firstName"); String lastName=ParamUtil.getString(actionRequest,"lastName"); double examFee=ParamUtil.getDouble(actionRequest,"examFee",00.00); String sex=ParamUtil.getString(actionRequest,"sex"); String[] subjects = ParamUtil.getParameterValues(actionRequest,"subjects",null); String acadamicYear=ParamUtil.getString(actionRequest,"acadamicYear"); String address=ParamUtil.getString(actionRequest,"address"); //Perepare Map object to send date to JSP Page to display Map<String,String> studentMapObject=new HashMap<String,String>(); studentMapObject.put("firstName", firstName); studentMapObject.put("lastName", lastName); studentMapObject.put("examFee", String.valueOf(examFee)); studentMapObject.put("sex", sex); studentMapObject.put("acadamicYear",acadamicYear); studentMapObject.put("address",address); //Send Map object to JSP page we wil use setAttribute(--) method on request object actionRequest.setAttribute("studentMapObject", studentMapObject);

JSP Page:

<% Map<String,String> studentMap=(Map<String,String>)renderRequest.getAttribute("studentMapObject"); if(studentMap!=null){ %> <b>First Name: </b><%=studentMap.get("firstName")%>    <br/> <b>Last Name:</b>  <%=studentMap.get("lastName")%><br/> <b>Exam Fee: </b> <%=studentMap.get("examFee")%><br/> <b>Gender: </b> <%=studentMap.get("sex")%><br/> <b>Acadamic Year: </b> <%=studentMap.get("acadamicYear")%><br/> <b>Address:  </b><%=studentMap.get("address")%><br/> <b>Subjects Obtained:</b><br/> <%}%>

Now we have done all the steps with respect to form submission and display data in other JSP page.

Navigate to other JSP page from Action Method

We will use following code to navigate other JSP page from action method.

actionResponse.setRenderParameter("mvcPath","/html/jsps/display_student.jsp");

Success/Error Messages

Generally when process some action we need to display success or error message based on result and it will be displayed in JSP page.

Add Success Message in Portlet Action Method

SessionMessages.add(actionRequest.getPortletSession(),"student-form-success");

Display Success Message in JSP Page

<%@page import="com.liferay.portal.kernel.servlet.SessionMessages"%> <%@ taglib uri="http://java.sun.com/portlet_2_0" prefix="portlet" %> <%@ taglib uri="http://liferay.com/tld/ui" prefix="liferay-ui" %> <% if(SessionMessages.contains(renderRequest.getPortletSession(),"student-form-success")){%> <liferay-ui:success key="student-form-success" message="Student form Submitted successfully and following are the details." /> <%} %>

Note:

We have used liferay UI tag library so we need add tag lib URI in jsp page.

SessionMessages class has many methods and you can have look into those methods.

Add Error Message in Portlet Action Method

SessionErrors.add(actionRequest.getPortletSession(),"student-form-error");

Display Error Message in JSP Page

<%@page import="com.liferay.portal.kernel.servlet.SessionErrors"%> <%@ taglib uri="http://java.sun.com/portlet_2_0" prefix="portlet" %> <%@ taglib uri="http://liferay.com/tld/ui" prefix="liferay-ui" %> <% if(SessionErrors.contains(renderRequest.getPortletSession(),"student-form-error")){%> <liferay-ui:error key="student-form-error" message="Student form Submitted have problem Please try again." /> <%} %>

Note:

We have sued liferay UI tag library so we need add tag lib URI in jsp page.

SessionErrors class has many methods you can have look into those methods.

Complete Example of Student Liferay MVC Portlet

Portlet Action Class and Action Method

package com.meera.liferaymvc; import java.io.IOException; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import javax.portlet.ActionRequest; import javax.portlet.ActionResponse; import javax.portlet.PortletException; import com.liferay.portal.kernel.servlet.SessionErrors; import com.liferay.portal.kernel.servlet.SessionMessages; import com.liferay.portal.kernel.util.ListUtil; import com.liferay.portal.kernel.util.ParamUtil; import com.liferay.util.bridges.mvc.MVCPortlet; public class StudentMVCPortletAction extends MVCPortlet {        public void addStudent(ActionRequest actionRequest,                      ActionResponse actionResponse) throws IOException, PortletException {               try{               String firstName = ParamUtil.getString(actionRequest, "firstName");               String lastName = ParamUtil.getString(actionRequest, "lastName");               double examFee = ParamUtil.getDouble(actionRequest, "examFee", 00.00);               String sex = ParamUtil.getString(actionRequest, "sex");               String[] subjects = ParamUtil.getParameterValues(actionRequest,                            "subjects", null);               String acadamicYear = ParamUtil                            .getString(actionRequest, "acadamicYear");               String address = ParamUtil.getString(actionRequest, "address");               // Perepare Map object to send date to JSP Page to display               Map<String, String> studentMapObject = new HashMap<String, String>();               studentMapObject.put("firstName", firstName);               studentMapObject.put("lastName", lastName);               studentMapObject.put("examFee", String.valueOf(examFee));               studentMapObject.put("sex", sex);               studentMapObject.put("acadamicYear", acadamicYear);               studentMapObject.put("address", address);               // Send Map object to JSP page we wil use setAttribute(--) method on               // request object               actionRequest.setAttribute("studentMapObject", studentMapObject);               // We have multiple subjects so we will send it seperate request               // attribute               List<String> subjectsList = new ArrayList<String>();               // for flexible manipulation we will convert noram array i.e subject               // array to List               subjectsList = ListUtil.toList(subjects);               actionRequest.setAttribute("subjectsList", subjectsList);               // we will display all student information in display_student.jsp so we               // will use setRenderParameter method on response object               // addding success message               SessionMessages.add(actionRequest.getPortletSession(),                            "student-form-success");               actionResponse.setRenderParameter("mvcPath",                            "/html/jsps/display_student.jsp");               }catch(Exception e){                      SessionErrors.add(actionRequest.getPortletSession(),"student-form-error");                      e.printStackTrace();                                    }        } }

Student Form JSP Page

<%@ taglib uri="http://java.sun.com/portlet_2_0" prefix="portlet" %> <portlet:defineObjects /> <portlet:actionURL var="addStudentActionURL" windowState="normal" name="addStudent"> </portlet:actionURL> <h2>Student Form</h2> <form action="<%=addStudentActionURL%>" name="studentForm"  method="POST"> <b>First Name</b><br/> <input  type="text" name="<portlet:namespace/>firstName" id="<portlet:namespace/>firstName"/><br/> <b>Last Name</b><br/> <input type="text" name="<portlet:namespace/>lastName" id="<portlet:namespace/>lastName"/><br/> <b>Exam Fee</b><br/> <input type="text" name="<portlet:namespace/>examFee" id="<portlet:namespace/>examFee"/><br/> <b>Gender</b><br/> <input type="radio" name="<portlet:namespace/>sex" value="male">Male<br> <input type="radio" name="<portlet:namespace/>sex" value="female">Female<br/> <b>Subjects Obtained</b><br/> <input type="checkbox" name="<portlet:namespace/>subjects" value="Maths">Maths<br> <input type="checkbox" name="<portlet:namespace/>subjects" value="Physics">Physics<br> <input type="checkbox" name="<portlet:namespace/>subjects" value="Chemistry">Chemistry<br> <input type="checkbox" name="<portlet:namespace/>subjects" value="Bio Technology">Biotechnology<br> <input type="checkbox" name="<portlet:namespace/>subjects" value="Computer Science">Computer Science<br> <b>Academic Year</b><br> <select name="<portlet:namespace/>acadamicYear">   <option value="I Year">I Year</option>   <option value="II Year">II Year</option>   <option value="III Year">III Year</option>   <option value="IV Year">IV Year</option> </select><br> <b>Address</b><br/> <textarea rows="4" cols="50" name="<portlet:namespace/>address"> </textarea><br/> <input type="submit" name="addStudent" id="addStudent" value="Add Student"/> </form>

Display Student Details JSP page.

<%@page import="com.liferay.portal.kernel.servlet.SessionErrors"%> <%@page import="com.liferay.portal.kernel.servlet.SessionMessages"%> <%@page import="java.util.List"%> <%@page import="java.util.Map"%> <%@ taglib uri="http://java.sun.com/portlet_2_0" prefix="portlet" %> <%@ taglib uri="http://liferay.com/tld/ui" prefix="liferay-ui" %> <portlet:defineObjects /> <portlet:renderURL var="addStundentRenderURL" windowState="normal"> </portlet:renderURL> <h2>Display Student Details</h2><br/> <a href="<%=addStundentRenderURL.toString()%>">Add Student</a><br/> <% if(SessionMessages.contains(renderRequest.getPortletSession(),"student-form-success")){%> <liferay-ui:success key="student-form-success" message="Student form Submitted successfully and following are the details." /> <%} %> <% if(SessionErrors.contains(renderRequest.getPortletSession(),"student-form-error")){%> <liferay-ui:error key="student-form-error" message="Student form Submitted have problem Please try again." /> <%} %> <% Map<String,String> studentMap=(Map<String,String>)renderRequest.getAttribute("studentMapObject"); if(studentMap!=null){ %> <b>First Name: </b><%=studentMap.get("firstName")%>    <br/> <b>Last Name:</b>  <%=studentMap.get("lastName")%><br/> <b>Exam Fee: </b> <%=studentMap.get("examFee")%><br/> <b>Gender: </b> <%=studentMap.get("sex")%><br/> <b>Acadamic Year: </b> <%=studentMap.get("acadamicYear")%><br/> <b>Address:  </b><%=studentMap.get("address")%><br/> <b>Subjects Obtained:</b><br/> <%}%> <% List<String> subjectsList=(List<String>)renderRequest.getAttribute("subjectsList"); if(subjectsList!=null){ for(String subject:subjectsList){ %> <%=subject%><br/> <%}}%>

Portlet Screens:

Screen: 1

Screen: 2

Portlet Download Link

https://sourceforge.net/projects/meeralferay/files/StudentLiferayMVCFormSubmission/

Note:

In the above example I just used simple html tags and normal code in entire portlet development. 

In future article we will use AUI tags and AUI java script to develop same portlet.

Author

Meera Prince

Liferay Top Contributor Award Winner

http://www.liferaysavvy.com

Read More