ajax實(shí)現(xiàn)用戶名校驗(yàn)的傳統(tǒng)和jquery的$.post方式(實(shí)例講解)

%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
!DOCTYPE html>
html>
head>
meta charset="UTF-8">
title>用戶注冊(cè)/title>
link rel="stylesheet" type="text/css" href="${pageContext.request.contextPath }/css/login.css" rel="external nofollow" >
script type="text/javascript">
//第三步：ajax異步請(qǐng)求用戶名是否存在
 function checkUsername(){
// 獲得文本框值:
var username = document.getElementById("username").value;
// 1.創(chuàng)建異步交互對(duì)象
var xhr = createXmlHttp();//第二步中已經(jīng)創(chuàng)建xmlHttpRequest,這里直接調(diào)用函數(shù)就可以了。
// 2.設(shè)置監(jiān)聽
xhr.onreadystatechange = function(){
if(xhr.readyState == 4){
if(xhr.status == 200){

//把返回的數(shù)據(jù)放入到span中
document.getElementById("span").innerHTML = xhr.responseText;//responseText是后臺(tái)返回的數(shù)據(jù)
}
}
}
// 3.打開連接
xhr.open("GET","${pageContext.request.contextPath}/user_findByName.action?time="+new Date().getTime()+"username="+username,true);
// 4.發(fā)送
xhr.send(null);
} 


//第二部：創(chuàng)建xmlHttp對(duì)象
function createXmlHttp(){
var xmlHttpRequest;
try{ // Firefox, Opera 8.0+, Safari
xmlHttp=new XMLHttpRequest();
}
catch (e){
try{// Internet Explorer
xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
}
catch (e){
try{
xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
}
catch (e){}
}
}
return xmlHttpRequest;
} 
function change(){
var img1 = document.getElementById("checkImg");
img1.src="${pageContext.request.contextPath}/checkImg.action?"+new Date().getTime();
}
/script>
/head>
body>
form action="${pageContext.request.contextPath }/user_regist.action" method="post" onsubmit="return checkForm()";>
div class="regist">
div class="regist_center">
div class="regist_top">
div class="left fl">會(huì)員注冊(cè)/div>
div class="right fr">a href="${pageContext.request.contextPath }/index.jsp" rel="external nofollow" target="_self">小米商城/a>/div>
div class="clear">/div>
div class="xian center">/div>
/div>
div class="regist_main center">

//第一步：首先，我們創(chuàng)建一個(gè)用戶名input輸入框，并添加一個(gè)onblur="checkUsername()"事件
div class="username">用nbsp;nbsp;戶nbsp;nbsp;名:nbsp;nbsp;input class="shurukuang" type="text" id="username" name="username" onblur="checkUsername()"/>span id="span">/span>/div>
div class="username">密nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;碼:nbsp;nbsp;input class="shurukuang" type="password" id="password" name="password"/>/div>	
div class="username">確認(rèn)nbsp;密碼:nbsp;input class="shurukuang" type="password" id="repassword" name="repassword" />/div>
div class="username">郵nbsp;nbsp;箱nbsp;nbsp;號(hào):nbsp;nbsp;input class="shurukuang" type="email" id="email" name="email" />/div>
div class="username">姓nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;名:nbsp;nbsp;input class="shurukuang" type="text" id="name" name="name"/>/div>
div class="username">手nbsp;nbsp;機(jī)nbsp;nbsp;號(hào):nbsp;nbsp;input class="shurukuang" type="text" id="phone" name="phone"/>/div>
div class="username">地nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;址:nbsp;nbsp;input class="shurukuang" type="text" id="addr" name="addr"/>/div>
div class="username">
div class="left fl">驗(yàn)nbsp;nbsp;證nbsp;nbsp;碼:nbsp;nbsp;input class="yanzhengma" type="text" id="checkcode" name="checkcode" maxlength="4"/>/div>
div class="right fl">img id="checkImg" class="captchaImage" src="${pageContext.request.contextPath}/checkImg.action" onclick="change()" title="點(diǎn)擊更換驗(yàn)證碼">/div>
div class="clear">/div>
/div>
/div>
div class="regist_submit">
input class="submit" type="submit" name="submit" value="立即注冊(cè)" >
/div>	
/div>
/div>
/form>
/body>
/html>

//ajax異步請(qǐng)求用戶名是否存在
$(function(){
$('#username').change(function(){//給username添加一個(gè)change事件
var val = $(this).val();//獲取輸入框的值
val = $.trim(val);//去空
if(val != ""){//判斷值是否為空
var url = "${pageContext.request.contextPath}/user_findByName.action";//url還是那個(gè)URL
var args ={"time":new Date().getTime(),"username":val};//這里和上面不同的是，這里用json方式實(shí)現(xiàn)傳入的time和username參數(shù)
$.post(url,args,function(data){//發(fā)送post請(qǐng)求，后臺(tái)返回的數(shù)據(jù)在data里面，
$('#span').html(data);//把后臺(tái)返回的數(shù)據(jù)放入span中
});
}	
});
})

public class UserAction extends ActionSupport implements ModelDrivenUser> {
private static final long serialVersionUID = 1L;
/**
* 模型驅(qū)動(dòng)
*/
private User user = new User();

 

@Override
public User getModel() {

 

return user;
}

// 注入U(xiǎn)serService
private UserService userService;

public void setUserService(UserService userService) {
this.userService = userService;
}

/**
* AJAX進(jìn)行異步校驗(yàn)用戶名的執(zhí)行方法
* 
* @throws IOException
*/
public String findByName() throws IOException {
User existUser = userService.findByName(user.getUsername());//調(diào)用service層的方法返回?cái)?shù)據(jù)庫中查詢出來的對(duì)象
// 獲得response對(duì)象,向頁面輸出:
HttpServletResponse response = ServletActionContext.getResponse();
response.setContentType("text/html;charset=UTF-8");//設(shè)置編碼格式
// 判斷返回的對(duì)象是否為空
if (existUser != null) {
// 如果有，查詢到該用戶:用戶名已經(jīng)存在
response.getWriter().println("用戶名已經(jīng)存在");
} else {
// 如果沒有，用戶名可以使用
response.getWriter().println("font color='green'>用戶名可以使用/font>");
}
return NONE;//此處返回空
}