Sample Programs And Applications

Liferay Hello World Portlet | How To Create Portlet Using Liferay Plugins SDK?

noreply@blogger.com (Tejash (તેજશ)) — Mon, 13 Jun 2011 06:38:00 -0700

In this post we will create and deploy a simple "hello world" portlet using the Liferay Plugins SDK using step by step guide as follows.

Initial Setup

Install Java Development Kit JDK 1.5 or higher, and set JAVA_HOME environment variable point to installation home directory of JDK, (Click here to know how to setup environment variable on different operating systems like windows / Unix / Linux platforms)

For Windows, right click on My Computer -> Properties -> Advanced -> Environment Variables here you can add or edit windows environment variables e.g. if JDK is installed at "c:\program files\sun\jdk1.5" then set JAVA_HOME to "c:\program files\sun\jdk1.5"
For Unix or Linux platforms go to home directory of user and add entry to set variable and export it in hidden file named .profile
For example,
```
 
    JAVA_HOME=/usr/lib/java/java-1.5
    export JAVA_HOME
```

Add JAVA_HOME/bin directory to PATH environment variable. i.e. for windows set value of PATH to %JAVA_HOME%\bin;%PATH% and for Unix and Linux platforms set its value to $JAVA_HOME/bin:$PATH
```
 
    export PATH=$JAVA_HOME/bin:$PATH
    
```
Install ANT 1.7 or higher and set ANT_HOME environment variable value to ANT installation directory.
Install Liferay portal with you choice of Application server (Click here for guideline to setup liferay portal and different platforms and application servers)
Install Liferay Plugin SDK (Visit here to know guideline to install Liferay plugins SDK)

Steps for creating portlet using Liferay Plugins SDK
Creating portlets with the Plugins SDK is extremely simple. There is a portlets folder inside of the Plugins SDK folder. This is where your portlet projects will reside. To create a new portlet, first decide what its name is going to be. You need both a project name (without spaces) and a display name (which can have spaces).
When you have decided on your portlet's name, you are ready to create the project. For the greeting portlet, the project name is “hello-word”, and the portlet title is “Hello World”. Navigate to the portlets directory in the terminal and enter the following command

For Linux, Unix and Mac OS X:

./create.sh hello-word "Hello World"

For all windows platforms:

create.bat hello-word "Hello World"

You should get a BUILD SUCCESSFUL message from Ant, and there will now be a new folder inside of the portlets folder in your Plugins SDK. This folder is your new portlet project. This is where you will be implementing your own functionality. Notice that the Plugins SDK automatically appends “-portlet” to the project name when creating this folder. In this case you can find directory "hello-word-portlet" in side portlets directory

Deploying the portlet on Liferay Portal

Make sure your Liferay Portal is already running or else you can start it by starting containing application server.
To deploy open a terminal window in your portlets/hello-world-portlet directory and enter this command
```
 
     ant deploy
```
You should get a BUILD SUCCESSFUL message, which means that your portlet is now being deployed.

If you switch to the terminal window running Liferay, and wait for a few seconds, you should see the message “1 portlet for my-greeting-portlet is available for use.” If not, something is wrong and you should double check your configuration.

Go to your web browser and log in to the portal as explained earlier. Then mouse over Add at the top of the page, and click on More.

Select the Sample category, and then click Add next to Hello World. Your portlet should appear in the page below. Congratulations, you've just created your first portlet!

How to create Dynamic Web Project Eclipse?

noreply@blogger.com (Tejash (તેજશ)) — Thu, 9 Dec 2010 19:06:00 -0800

Dynamic Web Project is used to develop, debug and deploy dynamic web applications in eclipse. For this project you need to have Eclipse IDE for Java EE developers which can be downloaded from here

Note: for my tutorial I am using Eclipse 3.6 Java EE IDE.

Steps to create Dynamic Web Project in Eclipse.
Step 1: Launch Dynamic Web Project Wizard.

If you are in the Java EE perspective then you can simply do it form File menu by going to File -> New -> Dynamic Web Project

If you are in any other perspective and there is no direct option in File menu to create Dynamic Web Project then go to File -> New -> Project that will launch project selection wizard
In this wizard select Dynamic Web Project under Web category and click Next
That will show the Dynamic Web Project wizard as follows:
Enter the Project Name
Select the Target Runtime from the list if does not exist then add new target runtime by clicking New Runtime... button. Here from the list of the list of Runtime select your server's runtime e.g. I selected Apache Tomcat v6.0

Click next to specify the server configuration, where you can specify the name, location and JRE for the server runtime and click on Finish button

Now you will come back to first page of the Dynamic Web Project wizard. Here select Dynamic Web module version to 2.4 or higher and leave all the other parameters as default values though you can change them as per your need

Click on the Next button to configure source location and Default output folder similar to Java Project
By default source location would be src change that to WebContent/WEB-INF/src and by default the Default output folder would be build/classes change that to WebContent/WEB-INF/classes

Then click on Next button to configure Web Module for Dynamic Web Project. Here you can configure Context root, Context Directory and select check box to Generate web.xml deployment descriptor

Now hit the finish button and Dynamic Web Project gets created with following structure

And the auto generated web.xml looks as follows:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>HelloWorld</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
</web-app>

Now using this Dynamic Web Project you can create any dynamic web applications based on JSP, Servlet, Struts etc.

JSP Hello World

noreply@blogger.com (Tejash (તેજશ)) — Thu, 5 Aug 2010 00:52:00 -0700

This sample code or example displays "hello world" in the browser using JSP

JSP can be learned very easily. This is just the beginning to learn this exciting language. This simple page contains a JSP program and it outputs on browser in running state. This given program of JSP illustrates you how to print simple "Hello World!" string on the browser through the server side code (provided by JSP).

This program also contains HTML (Hypertext Markup Language) code for designing the page and the contents. Following code of the program prints the string "Hello World!" by using <%="Hello World!" %> while you can also print the string by using out.println("Hello World!") in the <% and %> JSP tags.

Here is the code of the program "hello.jsp":

<html>
 <head><title>Hello World JSP Page.</title></head>
 <body>
  <font size="10"><%="Hello World!" %></font>

 </body>
</html>

Running or Executing hello.jsp
Note You must install tomcat or any other web-server which supports JSP.
Here I will explain how can you run hello.jsp using tomcat.
- Put hello.jsp in the directory [tomcat install directory]/webapps/ROOT/
- Then start tomcat server using [tomcat install directory]/bin/startup.bat on Windows platforms or [tomcat install directory]/bin/startup.sh on Unix or Linux platforms.
- Now open you web-browser and open URL "http://localhost:8080/hello.jsp" and you can see "Hello World!" as output in your web-browser.

Java Servlet Hello World with Tomcat

noreply@blogger.com (Tejash (તેજશ)) — Tue, 3 Aug 2010 06:21:00 -0700

Hello World Java Servlet Example , Tutorial or Sample Program

This article will is for new-bee of Java Servlet. Here I will explain you how you can run your first hello world Servlet example on Tomcat.

First download and install tomcat and JDK on your machine.

Create following folder structure inside tomcat installation directory.
[tomcat install directory]/webapps/hello
[tomcat install directory]/webapps/hello/WEB-INF
[tomcat install directory]/webapps/hello/WEB-INF/classes
[tomcat install directory]/webapps/hello/WEB-INF/classes/test

Now using any text based editor write following java code using any editor and save the file as HelloServlet.java at [tomcat install directory]/webapps/hello/WEB-INF/classes/test

package test;

import java.io.*;

import javax.servlet.http.*;
import javax.servlet.*;

public class HelloServlet extends HttpServlet {
  public void doGet (HttpServletRequest req,
                     HttpServletResponse res)
    throws ServletException, IOException
  {
    PrintWriter out = res.getWriter();

    out.println("Hello, world!");
    out.close();
  }
}

After this go to command prompt and change directory to [tomcat install directory]/webapps/hello/WEB-INF/classesand give following command

javac -cp .\..\..\..\..\lib\servlet-api.jar test\HelloServlet.java

We should start understanding the servlets from the beginning. Lets start by making one program which will just print the "Hello World" on the browser. Each time the user visits this page it will display "Hello World" to the user.

As we know that the our servlet extends the HttpServlet and overrides the doGet() method which it inherits from the HttpServlet class. The server invokes doGet() method whenever web server recieves the GET request from the servlet. The doGet() method takes two arguments first is HttpServletRequest object and the second one is HttpServletResponse object and this method throws the ServletException.

Whenever the user sends the request to the server then server generates two obects, first is HttpServletRequest object and the second one is HttpServletResponse object. HttpServletRequest object represents the client's request and the HttpServletResponse represents the servlet's response.

Inside the doGet(() method our servlet has first used the setContentType() method of the response object which sets the content type of the response to text/html. It is the standard MIME content type for the Html pages. After that it has used the method getWriter() of the response object to retrieve a PrintWriter object. To display the output on the browser we use the println() method of the PrintWriter class.

Now configuring web.xml for deploying and running the Servlet. Create web.xml with following content at [tomcat install directory]/webapps/hello/WEB-INF directory

<web-app version="2.4" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/j2ee" xsi:schemalocation="http:/java.sun.com/dtd/web-app_2_3.dtd">
  <servlet>
    <servlet-name>hello</servlet-name>
    <servlet-class>test.HelloServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>hello</servlet-name>
    <url-pattern>/hello</url-pattern>
  </servlet-mapping>
</web-app>

Now just start tomcat server with default configuration and open following URL in your browser.

http://localhost:8080/hello/hello

You will see "Hello, world!" as an output in your browser.

Note: Before starting tomcat make sure you have set JAVA_HOME environment variable point to installation directory of JDK.

Explanation

The servlet-mapping tells Resin that the URL /hello should invoke the hello-world servlet.
The servlet tells Resin that hello-world uses the test.HelloWorld class and that the value of the greeting init parameter is Hello World.

HelloWorld.java contains the actual servlet code. It just prints a trivial HTML page filled with the greeting specified in the web.xml.

init() and destroy() are included mostly for illustration. Server will call init() when it starts the servlet and destroy before server destroys it.

Eclipse Java - Hello World Application / Program

noreply@blogger.com (Tejash (તેજશ)) — Tue, 31 Mar 2009 22:04:00 -0700

This article will create a Java project and a Java class in Eclipse that will print "Hello world!" in the console when run.

1) Open the Java Perspective
If you're not already in the Java perspective, in the main menu select Window > Open Perspective > Java or click on the "Click to Perform" link below.

2) Create a Java Project
Before creating a class, we need a project to put it in. In the main toolbar, click on the New Java Project button. Enter HelloWorld for the project name, then click Finish.

3) Create your HelloWorld Class
The next step is to create a new class. In the main toolbar again, click on the New Java Class button. Enter HelloWorld for the class name, select the checkbox to create the main() method, then click Finish.

4) Add a Print Statement
Now that you have your HelloWorld class, in the main() method, add the following statement:

System.out.println("Hello world!");

Then save your changes; the class will automatically compile upon saving.

5) Run your Java Application / Program
To run your application, right-click on your class in the Package Explorer and select Run As > Java Application. The Console view should appear at the bottom and display the "Hello, world!" output.

Congratulations! You have successfully created a Hello World application!

Core Java - Hello Word Program / Application

noreply@blogger.com (Tejash (તેજશ)) — Tue, 31 Mar 2009 21:40:00 -0700

Here is the first program / application in Java, which is known as Hello World! program / application of Java.

Steps:

Open Notepad or Textpad or any similar Text Editor
Create New file in that and write following code in that:


public class HelloWorld
{

 public static void main(String[] args)
 {
  System.out.println("Hello world!");
 }

}

Now save this file as HellowWorld.java (e.g you have saved at c:\test\HelloWorld.java) (In Java you should give file name as .java, in this case HelloWorld is the class name so we save it as HelloWorld.java)
Now go to Command prompt
Change the directory of the command prompt to where you have saved HelloWorld.java

e.g.
```
cd c:\test
```

Here type the command javac <java file name>

```
javac HelloWorld.java
```

This command will compile the Java file
Now to run this program give command java <class name which has main method>
```
java HelloWorld
```
This program will run and give output as follows:
```
Hello world!
```

Note

In the above program public class HelloWorld defines the class name in Java. Declaring public as access modifier means it is accessible outside.
The line public static void main(String[] args) is the method which will be called first by the JVM when your try to run any application or program is java.
We must declare this method as public since it will be called by JVM
We must declare this method static since JVM will call this method by class name
The main method always have arguments String[] this stores command line arguments if any