<script type="text/javascript">
$(function() {
$("#userNiName").blur(function() {
var val = $(this).val();
val = $.trim(val);
var $this = $(this);
if (val != "") {
//把当前节点后面的所有 font 兄弟节点删除
$this.nextAll("font").remove();
var url = "user_checkName";
var args = {
"userNiName" : val,
"time" : new Date()
};
$.post(url, args, function(data) {
//表示可用
if (data == "1") {
$this.after("<font color='green'>用户名可用!</font>");
}
//不可用
else if (data == "0") {
$this.after("<font color='red'>用户名已被注册!</font>");
}
//服务器错误
else {
alert("服务器错误!");
}
});
} else {
$(this).val("");
$this.focus();
}
});
})
</script> 

public class UserAction extends ActionSupport implements ModelDriven<User>{
private User user=new User();
private UserService userService;
private InputStream inputStream;
public InputStream getInputStream() {
return inputStream;
}
//检验用户昵称是否存在
public String checkName() throws UnsupportedEncodingException{
System.out.println("进入ajax检验");
String userNiName=user.getUserNiName();
if(userService.findUserByName(userNiName)==null){
inputStream=new ByteArrayInputStream("1".getBytes("UTF-8"));
}else{
inputStream=new ByteArrayInputStream("0".getBytes("UTF-8"));
}
return "ajax_succ";
}
@Override
public User getModel() {
return user;
}
public void setUserService(UserService userService) {
this.userService = userService;
}
} 

package com.wang.shop.user.dao;
import java.util.List;

import org.springframework.orm.hibernate4.support.HibernateDaoSupport;
import com.wang.shop.user.entity.User;
public class UserDao extends HibernateDaoSupport{
/**
* 通过用户昵称查询User
* @param userNiName
* @return
*/
public User findUserByName(String userNiName){
List<User> list = (List<User>) this.getHibernateTemplate().find("select u from User u where u.userNiName=?", userNiName);
if(list!=null&&list.size()>0){
System.out.println("list:"+list.get(0));
return list.get(0);
}
return null;
}
}

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
"http://struts.apache.org/dtds/struts-2.3.dtd">
<struts>
<package name="shop" namespace="/" extends="struts-default">
<!-- UserAction -->
<action name="user_*" class="userAction" method="{1}">
<result name="regist_succ">/WEB-INF/jspForUser/login.jsp</result>
<result type="stream" name="ajax_succ">
<param name="contentType">text/html</param>
<param name="inputStream">inputStream</param>
</result>
</action>
</package>
</struts> 

<!--docBase就是你的项目工程所在的全路径,path就是写你的项目名,reloadable="true",可以自动重新加载修改过的class文件-->
<Context debug="0" docBase="D:\Tomcat 7.0\webapps\SSH_shop01" path="/SSH_shop01" reloadable="true" />