0

Using Ajax after an year...please tell me what I'm missing:

JSP/Ajax File:

<%@ 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>
<script type="text/javascript">

	function login() {
		var xmlhttp;
		var username = document.getElementById('username').value;
		var queryString = "username="+username;
		if(window.XMLHttpRequest){
			xmlhttp = new XMLHttpRequest();
		}else{
			xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
		}
		xmlhttp.open("GET", "LoginServlet", true);
		xmlhttp.setRequestHeader("Content-type","application/x-www-form-urlencoded");
		alert(queryString);
		xmlhttp.send(queryString);
		xmlhttp.onreadystatechange = function(){
			if(xmlhttp.readyState == 4 && xmlhttp.status == 200){
				alert(xmlhttp.responseText);
			}
		};
	}
</script>
</head>
<body>
	<input type="text" name="username" id="username" />
	<input type="button" onclick="javascript:login()" value="login" />
</body>
</html>

Servlet:

package Servlets;

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

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    
    public LoginServlet() {
        super();

    }

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		System.out.println("Servlet Called");
		PrintWriter out = response.getWriter();
		response.setContentType("text/html");
		
		String queryString = request.getParameter("username").toString();
		out.println(queryString);
	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
	}

}

Thank You

3
Contributors
4
Replies
5
Views
5 Years
Discussion Span
Last Post by i_M_patil
0

I'd say you're missing an explanation of what the issue is.

haha yeah that is one...
Actually I'm getting a null pointer exception in Servlet at line 27:

String queryString = request.getParameter("username").toString();

Probably the way I'm using xmlhttp.send(queryString); in JavaScript is wrong, but not able to figure out.

0

delete line NO. 22 in jsp file ie xmlhttp.send(queryString);
as in get method u dont need this. This is reqd in POST method..
For passing parameter in get method use this
xmlhttp.open("GET", "LoginServlet?username="+username", true);

replace line NO 19 with this and ur code will work.
Lemme know anymore issues

This topic has been dead for over six months. Start a new discussion instead.
Have something to contribute to this discussion? Please be thoughtful, detailed and courteous, and be sure to adhere to our posting rules.