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Editorial Team
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Asked: 2026-05-31T11:58:24+00:00

It is a very basic request-response test. Browser sends hello from browser to servlet

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It is a very basic request-response test. Browser sends “hello from browser” to servlet using jQuery $.ajax API, and servlet receives this message, then create a JSON object using org.json.simple library and sends back to browser a JSON response with message “hello from server”.

I am running this on localhost and just assume my IP address is 123.123.12.123, the platform is Ubuntu, server is Tomcat 6.0, running in the Eclipse IDE.

Test 1. I start the server from Eclipse, open Firefox, enter http://localhost:8080/myproject/test.jsp, I can see servlet receives message and browser receives response, test passed.

Test 2. server is still running at the Eclipse at Ubuntu, I start Windows 7 guest machine from VirtualBox and the Firefox browser in the Windows 7, enter http://123.123.12.123:8080/myproject/test.jsp, works as I expected, test passed.

Test 3. server is still running at Eclipse at Ubuntu, open Internet Explorer 9 browser, give it address http://123.123.12.123:8080/myproject/test.jsp, nothing happens.
The debug gives me

Response HTTP/1.1 200 OK

Response body {“message”:”hello from server”}

The test.jsp is

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!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=UTF-8">
<title>Insert title here</title>
</head>
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.js" type="text/javascript"></script>
<script type="text/javascript" src="release/js/libs/json2.js"></script>
<script>
$(document).ready(function(){
    var request = ({"message":'Hello from browser'});
    var jsonobj=JSON.stringify(request);
    $.ajax({
        data: {para:jsonobj},
        dataType: 'json',
        url: './TestServlet',
        type: 'POST',
        success: function(jsonObj){
            alert(jsonObj.message);     
        },
        error: function() {
            alert('Ajax readyState: '+xhr.readyState+'\nstatus: '+xhr.status + ' ' + err);
        }
    });
});
</script>
<body>
</body>
</html>

The servlet code is

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 org.json.simple.JSONObject;
import org.json.simple.JSONValue;

/**
 * Servlet implementation class TestServlet
 */
public class TestServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public TestServlet() {
        super();
    }

    /**
     * @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 {

        request.setCharacterEncoding("utf8");
        response.setCharacterEncoding("utf8");
        response.setContentType("application/json"); 
        PrintWriter out = response.getWriter(); 
        JSONObject jsonObj = (JSONObject) JSONValue.parse(request.getParameter("para"));
        System.out.println(jsonObj.get("message"));         
        JSONObject obj = new JSONObject();
        obj.put("message", "hello from server");
        out.print(obj);

    }

}

Update:

After a closer look by change 

 error: function() {
            alert('Ajax readyState: '+xhr.readyState+'\nstatus: '+xhr.status + ' ' + err);
}

to

error: function(xhr,err) {
            alert('Ajax readyState: '+xhr.readyState+'\nstatus: '+xhr.status + ' ' + err);
        }

I got alert readyState:0 and status:0.
But I can see {“message”:”hello from server”} at Response body and
the response header is

Key Value
Response    HTTP/1.1 200 OK
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1 Answer

  1. Editorial Team

    IE caches AJAX requests aggressively (more than Firefox, Chrome, and Safari, anyway).
    Sometimes you need to set cache header controller when request. Like cache:false. I tried to fix your code like this

    request.setCharacterEncoding("utf8");
        //response.setCharacterEncoding("utf8");
        response.setContentType("application/json");
        PrintWriter out = response.getWriter();
        JSONObject jsonObj = (JSONObject) JSONValue.parse(request.getParameter("para"));
        System.out.println(jsonObj.get("message"));
        JSONObject obj = new JSONObject();
        obj.put("message", "hello from server");
        out.print(obj.toString());

    I changed your response content-type from application/json; charset=utf8 to just application/json and that worked.

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