index.jsp
<script type="text/javascript" src="js/xhr.js"></script>
<script type="text/javascript">
function check_userName(){
//1 获取Ajax请求对象
var xhr = getXhr();
//alert(xhr)
//2 创建请求
//alert(userName);
xhr.open("POST","loginAction",true);
xhr.setRequestHeader(‘content-type‘,‘application/x-www-form-urlencoded‘);
//4 回调函数
xhr.onreadystatechange =
function callBack(){
if(xhr.readyState == 4 && xhr.status == 200){
var text = xhr.responseText;
//alert(text);
//将接受到的json字符串转换成json对象
var data = eval("("+text+")");
//取出json对象里面的userNameSpan属性值赋值给id的userNameSpan的span标签
document.getElementById("userNameSpan").innerHTML = data.userNameSpan;
}
}
//模拟网络延迟效果
document.getElementById("userNameSpan").innerHTML = "正在验证ing...";
//5 发送请求
var userName = document.getElementById("userName").value;
xhr.send("userName=" + userName);
}
//回调函数
</script>
</head>
<body>
userName:
<input id="userName" type="text" name="userName" onblur="check_userName()"/>
<span id="userNameSpan" style="color:red"></span>
<br/>
passWord:
<input id="passWord" type="password" name="passWord"/>
<br/>
</body>
xhr.js
function getXhr(){
var xhr = window.XMLHttpRequest?new XMLHttpRequest():new ActiveXObject();
return xhr;
}
LoginAction.java
public String register(){
//模拟网络延迟
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
if("yangkang".equals(userName)){
userNameSpan = "该用户名已经被注册";
}else{
userNameSpan = "√";
}
return SUCCESS;
}
private String userName;
private String passWord;
private String userNameSpan;
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public String getPassWord() {
return passWord;
}
public void setPassWord(String passWord) {
this.passWord = passWord;
}
public String getUserNameSpan() {
return userNameSpan;
}
public void setUserNameSpan(String userNameSpan) {
this.userNameSpan = userNameSpan;
}
<struts> <package name="json" extends="json-default" namespace="/"> <action name="loginAction" class="com.yangkang.action.LoginAction" method="register"> <result type="json"></result> </action> </package> </struts>
jar包：
ezmorph-1.0.3.jar
json-lib-2.1-jdk15.jar
struts2-json-plugin-2.2.3.1.jar
commons-logging-1.1.1.jar
freemarker-2.3.16.jar
ognl-3.0.1.jar
xwork-core-2.2.3.1.jar
struts2-core-2.2.3.1.jar
commons-beanutils-1.7.0.jar
commons-lang-2.5.jar
commons-fileupload-1.2.2.jar
javassist-3.11.0.GA.jar
commons-io-2.0.1.jar
源码地址：http://pan.baidu.com/s/1c0EqLEg
原文：http://www.cnblogs.com/toLife/p/4579622.html