Solution to the Ajax return validation is always a way to eject error errors _ajax related

Send a simple case:
Front desk:

<%@ page language= "java" import= "java.util.*" pageencoding= "UTF-8"%> <! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" >  

Background:

public class Login_do extends HttpServlet {public 
  void doget (HttpServletRequest request, HttpServletResponse Response) 
      throws Servletexception, IOException { 
      this.dopost (request, response); 
  public void DoPost (HttpServletRequest request, httpservletresponse response) 
      throws Servletexception, IOException { 
    request.setcharacterencoding ("UTF-8");  
    Response.setcharacterencoding ("UTF-8"); 
    String name =request.getparameter ("name"); 
    String Password = request.getparameter ("password"); 
    String js = "{\" name\ ": name,\" password\ ":p Assword}"; 
    PrintWriter out = Response.getwriter (); 
    Jsonobject json = new Jsonobject (); 
    Json.put ("name", name); 
    Out.print (Json.tostring ()); 
    Response.getwriter (). Write (json.tostring ()); 

When you click on login:

Workaround: There are two possible ways to eject the error message:
First:URL error, the background is not directly to the value of
You can use Firefox's firebug to view: If you respond to information, this is not the problem, then there may be the second case :
Error returning data type:
In my case, the returned data was accidentally printed two times, so just delete one sentence:

Out.print (Json.tostring ()); 
Response.getwriter (). Write (json.tostring ());  

caused an error. The information displayed in Firebug is:

The above is for you to analyze the use of Ajax to return validation when the error always pops up, I hope to solve such problems to help.