Ajax验证用户名是否存在


<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
  String path = request.getContextPath();
  String basePath = request.getScheme() + "://"
      + request.getServerName() + ":" + request.getServerPort()
      + path + "/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Ajax实现验证用户名</title>
<script type="text/javascript" src="JS/jquery-1.8.3.min.js"></script>
<script type="text/javascript">
  $(function() {
    $("input[name=userName]").blur(function() {
      var name = $(this).val();
      if (null == name || "" == name) {
        $("#msg").html("用户名不能为空");
        return;
      }
      //使用呢jQueryAjax实现用户名验证
      $.ajax({
        url : "CheckUserNameServlet",//
        type : "post",
        data : {
          "name" : name  //这个是得到了index界面输入框的值
        },
        dataType : "JSON",    
        success : function(reault) {
          var flag = reault.flag;
          if ("true" == flag) {
            $("#msg").html("可用的用户名！！");
          } else {
            $("#msg").html("已经使用的用户名");
          }
        }
      });
    });
  });
</script>
</head>


<body>
  用户名：
  <input type="text" id="userName" name="userName" />
  <span id="msg"></span>
</body>
</html>


Servlet

package 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 CheckUserNameServlet extends HttpServlet {

   
  public void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
     response.setContentType("text/html;charset:utf-8");
     String name=request.getParameter("name");
     PrintWriter out = response.getWriter();
     if ("admin".equals(name)||"张三".equals(name)) {
    out.print("{\"flag\":\"false\"}");
  }else{
    out.print("{\"flag\":\"true\"}");
  }
     out.flush();
     out.close();
  }

   
  public void doPost(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {

     doGet(request, response);
  }

}