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Issue regarding a basic AJAX project

Greenhorn

Posts: 5

posted 13 years ago

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Hi,

I am a newbie learning AJAX. I have an issue making the code work. I would really appreciate if you could help me out. I did not use External JavaScript files. I have my servlet and the HTML file.

I am able to call the servlet with the given URL, I have used SOPs on the servlet to see that it is being called. I think the problem is with the response. When I call the 'callback()' function, the status of the req.readystate is never equal to 4.

The alert message informs me that the value is "one". That is reason why I do not proceed any further and cannot call the parseMessage() and setMessage() functions, which receive the request from the servlet and update the HTML.

This is my HTML file:

[color=green]<!DOCTYPE html 
        PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" 
        "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title>AjaxTest</title>
    <script type="text/javascript">

//Is this the issue??	
	function callback() {
	alert("callback method!");
		if (req.readyState == 4) {
			alert(req.readyState);
			if (req.status == 200) {
				alert(req.status);
			//It is not being called for some reason
				parseMessage();
			}
		}
	}

var req;

</script>
    <meta http-equiv="Content-Script-Type" content="text/javascript" />
</head>
<body onload='init();'>
<label>Enter</label>
 
<input type="text"
       size="20"  
       id="userid"
       name="id"
       onkeyup="validate();">
<div id="userIdMessage"></div>

</body>
</html> [/color]

The code for my servlet is:

package classExamples;

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.HashMap;

public class ValidateServlet extends HttpServlet {
    
    private ServletContext context;
    private HashMap users = new HashMap();
 
    public void init(ServletConfig config) throws ServletException {
        super.init(config);
        this.context = config.getServletContext();
        users.put("greg","account data");
        users.put("duke","account data");
    }

public void doGet(HttpServletRequest request, HttpServletResponse  response)
        throws IOException, ServletException {
		//users.put("greg","account data");
        //users.put("duke","account data");

String targetId = request.getParameter("id");
		System.out.println("Whoow! The I am calling the right servlet! Id= " +targetId);
		System.out.println(users.containsKey(targetId.trim()));
        if ((targetId != null) && users.containsKey(targetId.trim())) {
			System.out.println("why not here?");
            response.setContentType("text/xml");
            response.setHeader("Cache-Control", "no-cache");
            response.getWriter().write("<message>valid</message>"); 
        } else {
			System.out.println("here?")
            response.setContentType("text/xml");
            response.setHeader("Cache-Control", "no-cache");
            response.getWriter().write("<message>invalid</message>"); 
			System.out.println("sent well? I ges so!");
        }
    }
}[color=orange] [/color]

Bear Bibeault

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posted 13 years ago

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Are you using Firebug in Firefox or some other tool to monitor the request and response?

it will show you what's being sent and returned so you can try to narrow down where any problem lies.

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Rahul Bukkarayasamudram

Greenhorn

Posts: 5

posted 13 years ago

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Hi,

I appreciate your response. I have not used Firebug till now. I will try to play around with it.

Just by the way, this is my source:

http://java.sun.com/developer/technicalArticles/J2EE/AJAX/

- Rahul