使用ajax校验用户是否存在

来源：互联网发布：linux nginx域名解析编辑：程序博客网时间：2024/05/21 18:32

页面：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>    <title>My JSP 'ajax3.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"><!--<link rel="stylesheet" type="text/css" href="styles.css">--><script type="text/javascript">//创建异步对象function createXMLHttpRequest() {try {return new XMLHttpRequest();//大多数浏览器} catch (e) {try {return ActvieXObject("Msxml2.XMLHTTP");//IE6.0} catch (e) {try {return ActvieXObject("Microsoft.XMLHTTP");//IE5.5及更早版本} catch (e) {alert("您的浏览器不支持");throw e;}}}}window.onload = function() {// 获取文本框，给它的失去焦点事件注册监听var userEle = document.getElementById("usernameEle");userEle.onblur = function() {//1.得到异步对象var xmlHttp = createXMLHttpRequest();//2.打开连接//xmlHttp.open("POST", "<c:url value='/ValidateUsernameServlet'/>", true);xmlHttp.open("POST", "/Web/ValidateUsernameServlet", true);//3.设置请求头：Content-TypexmlHttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");//4.发送请求，给出请求体xmlHttp.send("username=" + userEle.value);//5.给xmlHttp的onreadystatechange事件注册监听xmlHttp.onreadystatechange = function() {if(xmlHttp.readyState == 4 && xmlHttp.status == 200) {//双重判断//获取服务器的响应，判断是否为1// 是：获取span，添加内容：“用户名已被注册”var text = xmlHttp.responseText;var span = document.getElementById("errorSpan");if(text == "1") {//得到span元素span.innerHTML = "用户名已被注册！";} else {span.innerHTML = "";}}};};};</script>  </head>    <body><h1>演示用户名是否被注册</h1><form action="" method="post">用户名：<input type="text" name="username" id="usernameEle"/><span id="errorSpan"></span><br/>密　码：<input type="password" name="password"/><br/><input type="submit" value="注册"/></form>  </body></html>

ValidateUsernameServlet

package com.java.servlet;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class ValidateUsernameServlet extends HttpServlet {protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {request.setCharacterEncoding("utf-8");response.setContentType("text/html; charset=utf-8");String username = request.getParameter("username");if(username.equals("itachi")) {response.getWriter().print("1");} else {response.getWriter().print("0");}}}

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