cast的有关问题，求教

cast的问题，求教
先是将user对象放入session，如下代码

Java code

session.setAttribute("userHBM",user)

Java code

User user = (User)request.getSession().getAttribute("userHBM")

Java code

]] Root cause of ServletException.java.lang.ClassCastException: com.test.user.User cannot be cast to com.test.user.User

Java code

package com.test.user;public class User {}