适合人群：Ajax和jQuery入门
回收Ajax实现用户名验证
利用jQuery给出提示信息
用户注册的时候，利用Ajax实现检测用户名是否已经被注册过，许多细节没有实现，给各人做个简朴普及。
<%@ 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"> <title>用户注册页面</title> <script src="https://libs.baidu.com/jquery/1.8.3/jquery.min.js"></script> <script type="text/javascript"> var xmlHttp; function createXMLHttpRequest(){ if(window.XMLHttpRequest){ xmlHttp = new XMLHttpRequest(); }else if(window.ActiveXObject){ xmlHttp = new ActiveXObject("Microsoft.XMLHttp"); } } function validate(account){ createXMLHttpRequest(); xmlHttp.open("Get","ValidateServlet?account="+account,true); xmlHttp.onreadystatechange = callback; xmlHttp.send(null); } function callback(){ if(xmlHttp.readyState==4){ if(xmlHttp.status==200){ var text = xmlHttp.responseText; if(text=="true"){ //document.getElementById("msg").innerHTML = "该手机号已经被注册过"; $("#msg").text("该手机号已经被注册"); $("#sub").attr("disabled","true");//添加disabled属性，让按钮不行用 }else{ //document.getElementById("msg").innerHTML = ""; $("#msg").text(""); $("#sub").removeAttr("disabled");//移除disabled属性，让按钮可用 } }else{ alert("请求失败，错误码="+xmlHttp.status); } } } function checkInfo(){ var account = $("#account").val(); var pwd1 = $("#pwd1").val(); var pwd2 = $("#pwd2").val(); if(account==""||account==null){ $("#msg").text("账号不能为空"); $("#sub").attr("disabled","true"); return false; } if(pwd1==""||pwd1==null||pwd2==""||pwd2==null||pwd1!=pwd2){ $("#info").text("暗码不能为空可能两次暗码纷歧致"); $("#sub").attr("disabled","true"); return false; } $("#msg").text(""); $("#info").text(""); $("#sub").removeAttr("disabled"); } function submit(){ checkInfo(); $("#reg").submit(); } </script> </head> <body> <form action="RegisterServlet" method="post"> 账号：<input type="text" onblur="validate(this.value);"> <span>请输入手机号</span><br> 暗码：<input type="password" onblur="checkInfo();"><br> 确认暗码：<input type="password" onblur="checkInfo();"> <span></span><br> <input type="button" value="提交"> </form> </body> </html>
下面是ValidateServlet模仿实现，没有做真正的数据库表数据检测，各人自行完成。
package com.ambow.servlet; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; @WebServlet("/ValidateServlet") public class ValidateServlet extends HttpServlet { private static final long serialVersionUID = 1L; public ValidateServlet() { super(); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { PrintWriter pw = response.getWriter(); String account = request.getParameter("account"); System.out.println("account"+account); if("123".equals(account)) { pw.print("true"); }else { pw.print("false"); } } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }
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