vogella.de

Eclipse WTP provides tools for developing standard Java web applications and Java EE applications. Typical web artifacts in a Java environment are HTML pages, XML files, webservices, servlets and JSPs. Eclipse WTP simplifies the creation these web artifacts and provides runtime environments in which these artifacts can be deployed, started and debugged.

Eclipse WTP supports all mayor webcontainer, e.g. Jetty and Apache Tomcat as well as the mayor Java EE application server. This tutorial uses Apache Tomcat as a webcontainer.

In Eclipse WTP you create "Dynamic Web Projects". These projects provide the necessary functionality to run, debug and deploy a Java web application. Therefore for the development of Java web application you create "Dynamic Web Projects" .

During development you will create your server. You can manager you server via the server view. To see if you data was persisted stop and restart the server. You can do this via the Windows -> Show View -> Servers -> Servers

The following shows where you can start, stop and restart your server.

We will create a servlet which works as a webpage counter. This servlet will keep track of the number of visitors of a webpage. The servlet will persists the number of visitors in a text file. Create a new "Dynamic Web Project" called "de.vogella.wtp.filecounter" by selecting File -> New -> Other -> Web -> Dynamic Web Project.

Press finished. If asked if you want to switch to the Java EE Perspective answer yes.

A new project has been created with the standard structure of a Java web application. The WEB-INF/lib directory will later hold all the JAR files that the Java web application requires.

Create a new package "de.vogella.wtp.filecounter.dao" .

Create the Java class which will provide the number of visitors write this value to a file.

				
package de.vogella.wtp.filecounter.dao;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;

public class FileDao {

	public int getCount() {
		int count = 0;
		// Load the file with the counter
		FileReader fileReader = null;
		BufferedReader bufferedReader = null;
		PrintWriter writer = null ; 
		try {
			File f = new File("FileCounter.initial");
			if (!f.exists()) {
				f.createNewFile();
				writer = new PrintWriter(new FileWriter(f));
				writer.println(0);
			}
			if (writer !=null){
				writer.close();
			}
			
			fileReader = new FileReader(f);
			bufferedReader = new BufferedReader(fileReader);
			String initial = bufferedReader.readLine();
			count = Integer.parseInt(initial);
		} catch (Exception ex) {
			if (writer !=null){
				writer.close();
			}
		}
		if (bufferedReader != null) {
			try {
				bufferedReader.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		return count;
	}

	public void save(int count) throws Exception {
		FileWriter fileWriter = null;
		PrintWriter printWriter = null;
		fileWriter = new FileWriter("FileCounter.initial");
		printWriter = new PrintWriter(fileWriter);
		printWriter.println(count);

		// Make sure to close the file
		if (printWriter != null) {
			printWriter.close();
		}
	}

}
			

Create a servlet. Right click on the folder Webcontent and select New-> Other. Select Web -> Servlet. Maintain the following data.

Press finish.

Maintain the following code for the servlet.

				
package de.vogella.wtp.filecounter.servlets;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import de.vogella.wtp.filecounter.dao.FileDao;

/**
 * Servlet implementation class FileCounter
 */
public class FileCounter extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
	int count;
	private FileDao dao;

	public void init() throws ServletException {
		dao = new FileDao();
		try {
			count = dao.getCount();
		} catch (Exception e) {
			getServletContext().log("An exception occurred in FileCounter", e);
			throw new ServletException("An exception occurred in FileCounter"
					+ e.getMessage());
		}
	}
	
	protected void doGet(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
		// Set a cookie for the user, so that the counter does not increate
		// everytime the user press refresh
		HttpSession session = request.getSession(true);
		// Set the session valid for 5 secs
		session.setMaxInactiveInterval(5);
		response.setContentType("text/plain");
		PrintWriter out = response.getWriter();
		if (session.isNew()) {
			count++;
		}
		out.println("This site has been accessed " + count + " times.");
	}

	public void destroy() {
		super.destroy();
		try {
			dao.save(count);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

}

			

This code will read the counter from a file on the server and return plain text to the browser. The servlet will increase the counter if the user was 5 seconds inactive.

Select your servlet, right-click on it and select Run As -> Run on Server.

Select your server and include your servlet so that is runs on the server.

Press finish. You should see the Eclipse internal web browser displaying your the count number. If you wait 5 seconds and refresh the number should increase.

Congratulations. You created your first working servlet with Eclipse WTP!

The following will demonstrate the creation and usage of a JaveServer Page . Create the Dynamic Web Project "de.vogella.wtp.jspsimple". and the package "de.vogella.wtp.jspsimple"

Select the folder "WebContent", right-mouse click -> New -> JSP and create the JSP "FirstJSP". Select the "New JSP File (html)" template.

Create the following coding.

				
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>JSP with the current date</title>
</head>
<body>
<%java.text.DateFormat df = new java.text.SimpleDateFormat("dd/MM/yyyy"); %>

<h1>Current Date: <%= df.format(new java.util.Date()) %> </h1>
</body>
</html>
			

Start your webapplication. You find your JSP under the URL "http://localhost:8080/de.vogella.wtp.jspsimple/FirstJSP.jsp".

Set the JSP page as the welcome page for your application. This is optional but make it easier because the JSP is automatically opened if the application is started. Modify the file "WebContent/WEB-INF/web.xml" to the following.

				
<?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>de.vogella.wtp.jspsimple</display-name>
  <welcome-file-list>
    <welcome-file>FirstJSP.jsp</welcome-file>
  </welcome-file-list>
</web-app>
			

This allows to start the JSP via the path ""http://localhost:8080/de.vogella.wtp.jspsimple".

This example will demonstrate the usage of JSPs for the display and a servlet as the controller for a web application. The servlet will dispatch the request to the correct JSP.

Create the Dynamic Web Project "de.vogella.wtp.jsp". and the package "de.vogella.wtp.jsp"

Create a new servlet "Controller" in the package "de.vogella.wtp.jsp.controller".

				
package de.vogella.wtp.jsp.controller;

import java.io.IOException;
import java.util.Map;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class Controller
 */
public class Controller extends HttpServlet {
	private static final long serialVersionUID = 1L;
	private static String DELETE_JSP = "/Delete.jsp";
	private static String EDIT_JSP = "/Edit.jsp";
	private static String SHOWALL_JSP = "/ShowAll.jsp";

	
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		String forward="";
		// Get a map of the request parameters
		@SuppressWarnings("unchecked")
		Map parameters = request.getParameterMap();
		if (parameters.containsKey("delete")){
			forward = DELETE_JSP;
		} else if (parameters.containsKey("edit")){
			forward = EDIT_JSP;
		} else {
			forward = SHOWALL_JSP;
		}
		RequestDispatcher view = request.getRequestDispatcher(forward);
		view.forward(request, response);
	}
}

			

This controller will check which parameters has been passed to the servlet and then forward the request to the correct JSP.

In the folder "WebContent" create the new JSP "ShowAll" with the following code.

				
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
	pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Show all names</title>
</head>
<body>


<form method="GET" action='Controller' name="showall">
<table>
	<tr>
		<td><input type="checkbox" name="id1" /></td>
		<td>Jim</td>
		<td>Knopf</td>
	</tr>
	<tr>
		<td><input type="checkbox" name="id2" /></td>
		<td>Jim</td>
		<td>Bean</td>
	</tr>
</table>

<p><input type="submit" name="delete" value="delete" />&nbsp; 
   <input type="submit" name="edit" value="edit" />&nbsp; 
	<input type="reset"
	value="reset" /></p>
</form>



</body>
</html>
			

Create the JSP "Delete.jsp".

				
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
	pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>

Delete successful
<form method="GET" action='Controller' name="delete_success"><input
	type="submit" value="back"></form>
</body>
</html>

			

Create the JSP "Edit.jsp".

				
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
	pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>


<form method="GET" action='Controller' name="edit">
<table>
	<tr>
		<td>First name:</td>
		<td><input type="text" name="firstName"></td>
	</tr>
	<tr>
		<td>Last name:</td>
		<td><input type="text" name="lastName"></td>
	</tr>
	<tr>
		<td><input type="submit" value="save"> <input
			type="reset" value="reset"> <input type="submit" value="back">
		</td>
	</tr>
</table>
</form>

</body>
</html>
			

Run your new application by running "ShowAll.jsp" on the server. You should be able to navigate between the pages.

Source Code of Examples

http://www.servlets.com/ Web page about servlets

http://www.windofkeltia.com/j2ee/wtp-tutorial.html Tutorial: Using the Eclipse Web Tools Platform with Apache Tomcat by Russell Bateman

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