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HTTP Form POST Request using AJAX and Servlet

Posted by Hitesh Agrawal
March 4, 2008

In Java World Servlets are popularly used for Model View Controller(MVC) Design Pattern. This article will guide you on writing AJAX based application that will post data to Servlet and will fetching the computed data from the Servlet. With this approach the page will get the updated content from the server without refreshing the jsp/html page.

JSP Code: 

<html>
<head>
<title>JSP and Servlet using AJAX</title>
<script type="text/javascript">
 
function getXMLObject()  //XML OBJECT
{
   var xmlHttp = false;
   try {
     xmlHttp = new ActiveXObject("Msxml2.XMLHTTP")  // For Old Microsoft Browsers
   }
   catch (e) {
     try {
       xmlHttp = new ActiveXObject("Microsoft.XMLHTTP")  // For Microsoft IE 6.0+
     }
     catch (e2) {
       xmlHttp = false   // No Browser accepts the XMLHTTP Object then false
     }
   }
   if (!xmlHttp && typeof XMLHttpRequest != 'undefined') {
     xmlHttp = new XMLHttpRequest();        //For Mozilla, Opera Browsers
   }
   return xmlHttp;  // Mandatory Statement returning the ajax object created
}
 
var xmlhttp = new getXMLObject();	//xmlhttp holds the ajax object
 
function ajaxFunction() {
  if(xmlhttp) { 
  	var txtname = document.getElementById("txtname");
    xmlhttp.open("POST","getname",true); //getname will be the servlet name
    xmlhttp.onreadystatechange  = handleServerResponse;
    xmlhttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
    xmlhttp.send("txtname=" + txtname.value); //Posting txtname to Servlet
  }
}
 
function handleServerResponse() {
   if (xmlhttp.readyState == 4) {
     if(xmlhttp.status == 200) {
       document.myForm.message.innerHTML=xmlhttp.responseText; //Update the HTML Form element 
     }
     else {
        alert("Error during AJAX call. Please try again");
     }
   }
}
</script>
<body>
<form name="myForm" method="POST" action="getname">
<table>
 <tr>
  <td>Enter Name</td>
  <td><input type="text" name="txtname" id="txtname" /></td>
 </tr>
 <tr>
  <td colspan="2"><input type="button" value="Submit"  onclick="ajaxFunction();" /></td>
 </tr> 
</table>
<div id="message"></div> 
</form>
</body>
</head>
</html>

Servlet Code

import java.io.*;
 
import java.text.*;
 
import java.util.*;
 
import javax.servlet.*;
 
import javax.servlet.http.*;
 
public class getname extends HttpServlet {
 
	public void init(ServletConfig config) throws ServletException {	
		super.init(config);
	}
 
	public void destroy() {
 
	}
 
	public void doPost(HttpServletRequest request,HttpServletResponse response) throws IOException, ServletException {
		String name = null;
		PrintWriter out = response.getWriter();
		if(request.getParameter("txtname") != null) {
			name = request.getParameter("txtname");
		}
                else {
                       name = "";
                }
  	        out.println("You have successfully made Ajax Call:" + name);
	}
}




Explanation for the AJAX Code

Here i have declared 3 JavaScript function:
getXMLObject() - Responsible for creating the AJAX Object depending on the browser.
ajaxFunction() - Responsible for calling servlet through AJAX call.
handleServerResponse() - Responsible for displaying the data retrieved from the server.

How the AJAX Code Works:

Explanation for the Servlet Code

Related Post

AJAX, Java

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Comments

Good site I “Stumbledupon” it today and gave it a stumble for you.. looking forward to seeing what else you have..later

Comment by Html Forms on April 8, 2008 @ 4:50 am
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