Jquery——Ajax实例

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<%@ 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>
<script src="js/jquery-1.6.4.js"type="text/javascript"></script>
<script type="text/javascript" src="js/find.js" ></script>
<script type="text/javascript">
$(function (){

$("#tb").click(function(){
check();

if($("#result").text()=="用户名已经存在"){
alert("用户名已经存在");
return false;
}
//$("#myform").submit();
});
});

</script>

    <base href="<%=basePath%>">

    <title>My JSP 'MyJsp.jsp' starting page</title>

<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">

</head>

<body>
<form action="" id="myform">
    <input type="text" id="username" onblur="check()"/>
    <div id="result"></div>

    <input type="submit" value="提交" id="tb" />
    </form>
</body>
</html>

Find.js——

function check(){
//获得文本框的值
var z=$("#username").val();
$.post("Check",{username:z},function(data){
$("#result").html(data);
})
}

Check类——

package com.ajax;

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 Check 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 {

  response.setContentType("text/html");
  response.setCharacterEncoding("utf-8");
  PrintWriter out = response.getWriter();
  String username=request.getParameter("username");
  if(username==null){
   out.print("用户名不能为空");
  }else
  if(username.equals("123")){
   out.print("用户名已经存在");
  }else{
   out.print("用户名不存在");
  }
  out.flush();
  out.close();
}

}