jquery ajax call returns error on successful call to a servlet

I have a servlet that adds a user to a file on the server side.

I invoke it with a jqueries ajax call.

I can see on the server that the method is being called correctly and my user is added, but the error callback is being invoked on the jquery call. All the status text says is error.

Using firebug the response seems to be empty. Why can I not get a success jquery callback?

//Servlet Code
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String action = request.getParameter("action");
    String responseStr = "";
    if(action.equals("addUser")) 
    {  
      responseStr = addUser(request);       
    }
    System.out.println("Reponse:" + responseStr);  
    response.setContentType("application/json"); 
    response.setCharacterEncoding("utf-8"); 
    response.getWriter().println(responseStr);
}

private String addUser(HttpServletRequest request) throws IOException
{
    Storage s;

    s = Storage.load();
    String name = request.getParameter("name");
    String imageUrl = request.getParameter("imageUrl");
    User u = new User();
    u.setName(name);
    u.setImageUrl(imageUrl);
    s.addUser(u);
    s.save();
    return "success";
}

.

//javascript code
function addUser() {
    var name = $('#name').val();
    var imageUrl = $('#imageUrl').val();
    var url = "http://ws06525:8080/QCHounds/QCHoundServlet?action=addUser&name=${name}&imageUrl=${imageUrl}";
    url = url.replace("${name}", name);
    url = url.replace("${imageUrl}", imageUrl);
    $('#resu开发者_JAVA百科lt').html(url);
    $.ajax({
      url: url,
      success: function( data ) {
         $('#result').html(data);
      },
      error: function(jqXHR, textStatus, errorThrown) 
      {
           alert("error: " + textStatus); 
           alert("error: " + errorThrown);
      }
    });


}

Aaargh! Feel like an idiot. It's a cross site scripting issue. I was testing the call to the server from the html file on disk so my browser address was

file://projects/myproject/content/Users.html <<< Fail

instead of:

http://myboxname:8080/appname/Users.html <<< Works

The actual code is fine...

use this for learn what is the problem, it will be better for get solution i think

error: function(e){
    alert(JSON.stringify(e))
}

For one thing the string "success" isn't valid json. If your ajax query is expecting json, that would fail it.

What if you returned "{ \"success\": true }" ?

EDIT

It looks like from your ajax call that the response shouldn't be json, why is your return content type json?

If it is true that firebug shows no response, your problem must be in the java code that writes the response.