项目目录:
req.jsp代码：
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<script type="text/javascript" src="${pageContext.request.contextPath }/js/myJS.js"></script>
<title>Insert title here</title>
</head>
<script type="text/javascript">
function ckName(){
//获取用户名
var name=document.getElementsByTagName("input")[0];
//创建XMLHttpRequest对象
var xhr=getXMLHttpRequest();
//处理结果
xhr.onreadystatechange=function(){
if(xhr.readyState==4)//请求正常
if(xhr.status==200){
//alert(xhr.responseText);//得到结果
var msg=document.getElementById("msg");
if(xhr.responseText=="true"){
msg.innerHTML="用户已存在";
}else{
msg.innerHTML="用户可以使用";
}
}
}
//创建连接
xhr.open("get","${pageContext.request.contextPath }/servlet/chNameServlet?name="+name.value);
//发送请求
xhr.send(null);
}
</script>
<body>
用户名<input type="text" name="username" onblur="ckName()"><span id="msg"></span><br>
密码<input type="password" name="pwd"/>
</body>
</html>ChNameServlet.java代码：
package com.haidi8.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 ChNameServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
PrintWriter out = response.getWriter();
String name = request.getParameter("name");
if("tom".equals(name)){
out.print(true);
}else{
out.print(false);
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
运行效果:
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