为嘛getobject=null

[shiner_suxin]

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub

String user_id=request.getParameter("abcde");
UserService userService=new UserService();
User user=userService.getUser(user_id);
if(user!=null)
{
System.out.println("查到用户！");
request.setAttribute("data", user);
request.getRequestDispatcher("/userInfoManager.jsp").forward(request, response);
}
else {
System.out.println("未查到用户！");
}
}
为什么执行userInfoManager.jsp时总会 出现 getobject=null 未查到用户！

[执笔记忆的空白]

UserService userService=new UserService(); User user=userService.getUser(user_id); 问题出在这，你看看是不是service实例的问题 ，或者是你这个userId在数据库查不到值

[shiner_suxin]

public User getUser(String user_id) { Connection connection = DBUtils.getConnection(); System.out.println("getobject="+user_id); String querySql="SELECT user_id,username,password,phone FROM T_user WHERE user_ID=?"; User user=new User(); try { PreparedStatement prepareStatement = connection.prepareStatement(querySql); prepareStatement.setString(1, user_id); ResultSet resultSet = prepareStatement.executeQuery(); String username=""; String password=""; String phone=""; if(resultSet.next()) { username=resultSet.getString(2); password=resultSet.getString(3); phone=resultSet.getString(4); System.out.println("username="+username); System.out.println("password="+password); System.out.println("phone="+phone); user.setUser_id(user_id); user.setUsername(username); user.setPassword(password); user.setPhone(phone); } resultSet.close(); prepareStatement.close(); connection.close(); if(username==""||username.equals("")) { return null; } else { return user; } } catch (SQLException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } return user; } 这是getUser方法，感觉也没啥问题，检查了一下t_user表中也有user_id这项,大神再帮看看

[丶顛簸人生]

debug一下问题不就解决了，看userService实例是不是null.如果不是null,那么User user=userService.getUser(user_id); 查询是不是null. 要学会利用debug