在java中应用ajax，验证用户名，前台用js处理

前台的注册页面

<%&＃64; page language&＃61;"java" import&＃61;"java.util.*" pageEncoding&＃61;"utf-8"%>
<%String path &＃61; request.getContextPath();String basePath &＃61; request.getScheme() &＃43; "://"&＃43; request.getServerName() &＃43; ":" &＃43; request.getServerPort()&＃43; path &＃43; "/";
%>


">




用户名:
密码:
个性签名:







后台的servlet


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;public class CheckNameServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String username &＃61; request.getParameter("username");System.out.println(username);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String username &＃61; request.getParameter("username");String password &＃61; request.getParameter("password");System.out.println(username);System.out.println(password);String msg &＃61; "";if (username.equals("admin")) {// 用户已存msg &＃61; "{\"content\":\"用户已存在\",\"flag\":true}";} else {// 用户不存在msg &＃61; "{\"content\":\"用户不存在\",\"flag\":false}";}response.getWriter().write(msg);}}