How Ajax works with java example
Introducing AJAX : asynchronous java and xml for Java web application , Here is a simple example
The below example shows you how java servlet response/replies to ajax request/call from a jsp page. The java server page need not be reload again, only the div refresh. Please try the source code.
Deployement Descriptor : web.xml
<?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>Java ajax call</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>nextgeneration.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>
<servlet>
<description></description>
<display-name>ForAjax</display-name>
<servlet-name>ForAjax</servlet-name>
<servlet-class>ForAjax</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>ForAjax</servlet-name>
<url-pattern>/ForAjax</url-pattern>
</servlet-mapping>
</web-app>
XXX XXX XXX XXX XXX XXX XXX XXX XXX XXX XXX
index.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>Nexegen Technologies</title>
<script type="text/javascript" src="ajax.js"></script>
</head>
<body>
<div id="ajaxDiv">
</div>
<div id = "mydiv">
<input type="button" onclick="verifyPassword()">
</div>
</body>
</html>
XXX XXX XXX XXX XXX XXX XXX XXX XXX
Ajax.js /*
* creates a new XMLHttpRequest object which is the backbone of AJAX,
* or returns false if the browser doesn't support it
*/
function getXMLHttpRequest() {
var xmlHttpReq = false;
// to create XMLHttpRequest object in non-Microsoft browsers
if (window.XMLHttpRequest) {
xmlHttpReq = new XMLHttpRequest();
} else if (window.ActiveXObject) {
try {
// to create XMLHttpRequest object in later versions
// of Internet Explorer
xmlHttpReq = new ActiveXObject("Msxml2.XMLHTTP");
} catch (exp1) {
try {
// to create XMLHttpRequest object in older versions
// of Internet Explorer
xmlHttpReq = new ActiveXObject("Microsoft.XMLHTTP");
} catch (exp2) {
xmlHttpReq = false;
}
}
}
return xmlHttpReq;
}
/*
* AJAX call starts with this function
*/
function verifyPassword() {
var xmlHttpRequest = getXMLHttpRequest();
xmlHttpRequest.onreadystatechange = getReadyStateHandler(xmlHttpRequest);
xmlHttpRequest.open("POST", "ForAjax", true);
xmlHttpRequest.setRequestHeader("Content-Type",
"application/x-www-form-urlencoded");
xmlHttpRequest.send(null);
}
/*
* Returns a function that waits for the state change in XMLHttpRequest
*/
function getReadyStateHandler(xmlHttpRequest) {
// an anonymous function returned
// it listens to the XMLHttpRequest instance
return function() {
if (xmlHttpRequest.readyState == 4) {
if (xmlHttpRequest.status == 200) {
document.getElementById("ajaxDiv").innerHTML = xmlHttpRequest.responseText;
} else {
alert("HTTP error " + xmlHttpRequest.status + ": " + xmlHttpRequest.statusText);
}
}
};
}XXX XXX XXX XXX XXX XXX XXX XXX XXX XXXservlet class :ForAjax
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class ForAjax
*/
public class ForAjax extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public ForAjax() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println(" Konzern .... ");
response.setContentType("text/html");
response.getWriter().write(" success");
}
}
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