JQuery验证jsp页面属性是否为空(实例代码)

<form action="./login.action" method="post" onsubmit="return check();">
<table>
<tr>
<td width="451"> </td>
<td width="378">

<table >
<tr>
<td width="60"> </td>
<td>
<font color="#000000">用户名：</font>
</td>
<td align="left"> <input name="userInfo.userName" id="userName" type="text">
<span id="checkUserName"></span>
</td>
<tr> <td> </td>
<td align="right" nowrap>
<font color="#000000">密 码：</font>
</td>
<td align="left">
<input name="userInfo.password" id="password" type="password">
<span id="checkPassword"></span>
</td>
</tr>
<tr>
<td colspan="4" align="center" nowrap>
<input type="submit" id="btnLog" value=" 登 录 " >
   <input type="reset" value=" 重 置 ">
</td>
</tr>
</table>
</form>

<script type="text/javascript" src="js/common/jquery-1.5.1.min.js"></script>

<script type="text/javascript">
function check(){
var userName=$("#userName").val();
var password=$("#password").val();
alert(userName);
alert(password);
if(userName==""){
$("#checkUserName").html("<font color='red'>用户名不能为空！</font>");
return false;
}
if(password==""){
$("#checkPassword").html("<font color='red'>密码不能为空！</font>");
return false;
}
return true;
}
</script>