为什么传值出现这样的错误！！！
只要在刷新一次就变成正常的了
servlet里
String id = request.getParameter("userId");
if(action.equals("modify")){
User u = userBiz.searchByName(id);
request.setAttribute("users", u);
request.getRequestDispatcher("manage/user-modify.jsp").forward(request, response);
}
jsp页面
<form action="UserUpdate" method="post">
<table class="form">
<tr>
<td class="field">用户名：</td>
<td><input type="text" class="text" name="userName"
value="${requestScope.users.userId }" readonly="readonly" />
</td>
</tr>
<tr>
<td class="field">姓名：</td>
<td><input type="text" class="text" name="name"
value="${requestScope.users.userName }" />
</td>
</tr>
<tr>
<td class="field">密码：</td>
<td><input type="password" class="text" name="passWord"
value="${requestScope.users.password }" />
</td>
</tr>
<tr>
<td class="field">性别：</td>
<td><input type="radio" name="sex" value="男 "
<c:if test="${requestScope.users.sex=='男 '}">
<c:out value="checked"></c:out>
</c:if>
/>
男
<input type="radio" name="sex" value="女 "
<c:if test="${requestScope.users.sex=='女 '}">
<c:out value="checked"></c:out>
</c:if> />
女
</td>
</tr>
<tr>
<td class="field">出生日期：</td>
<td><input type="text" class="text" name="date"
value=" ${requestScope.users.birthday}" />
</td>
</tr>
<tr>
<td class="field">电子邮件：</td>
<td><input type="text" class="text" name="email"
value="${requestScope.users.email}" />
</td>
</tr>
<tr>
<td class="field">手机号码：</td>
<td><input type="text" class="text" name="mobile"
value="${requestScope.users.mobile}" />
</td>
</tr>
<tr>
<td class="field">送货地址：</td>
<td><input type="text" class="text" name="address"
value="${requestScope.users.address}" />
</td>
</tr>
<tr>
<td></td>
<td><label class="ui-blue"><input type="submit"
name="submit" value="更新" /> </label>
</td>
</tr>
</table>
</form>
------解决方案--------------------------------------------------------
出现什么样错误了？
想问什么？
------解决方案--------------------------------------------------------
楼上问的话,我也想问一次,出什么问题了,