struts+ajax验证注册用户名是否存在

@Override
public boolean check(User user) throws Exception {
Map<String, Object> map = new HashMap<String, Object>();
Integer id = 0;
session=super.getSession();
Transaction tx = session.beginTransaction();
if (new UserDaoImpl().findUserByuserNum(user)) {// 用户存在.不可以注册
flag = false;
map.put("msg", "用户名已存在");
} else {// 用户不存在，可以注册
flag = true;
//			session.save(user);
//			tx.commit();
}
releaseSession(session);
return flag;
}

public String userCheck() throws Exception{
//		System.out.println("userNum="+user.getUserNum());
//		System.out.println("password="+user.getPassword());
if(osDao.findUserByuserNum(user)){
System.out.println("用户名已存在");
msg="true";
result="success";

}else{
System.out.println("用户名不存在");
msg="false";
result="input";
}
return result;
}

<package name="house-json" extends="json-default">
<action name="UserAction_*" class="UserAction"
method="{1}">
<result name="success" type="json"></result>
<result name="error" type="json"></result>
</action>
</package>

<form action="UserAction_Doregister" method="post" id="register_form">
<table width="90%" border="0" cellspacing="0" cellpadding="0">
<tr>
<td align="right" width="30%">用户名(工号)：</td>
<td align="left"><input type="text" name="user.userNum"
id="userNum" onblur="register();"/></td>
<td id="msg"></td>
</tr>
<tr>
<td align="center" colspan="3"><span id="msg"></span> <br />
<input type="button" value="提交" onclick="register('submit');" />
<input type="reset" value="重置" /></td>
<input type="button" value="提交1" id='add'" />
</tr>
</table>
</form>

function register(tag) {
var name = $("#userNum").val();
var pw = $("#password").val();
var nickName = $("#nickname").val();
var age = $("#age").val();
var sex = $("#sex").val();
var mobile = $("#mobile").val();
var address = $("#address").val();
var url='userCheck?user.userNum='+name+'&user.password='+pw;
$.ajax({
url:url,
dataType:"json",
success:function(data){
alert(data);
if(data=='false'){
if(tag=='submit'){
alert(tag);
$("#register_form").submit();
$(".action").load("user_list.jsp", function(responseText) {
$(".action").html(responseText);
})
}else{
$("#msg").html("用户名可以使用");
$("#msg").css("color","green");
}
}else{
$("#msg").html("用户名已存在");
$("#msg").css("color","red");
}
}
});
}