登陆校验一直跳转到失败页面

package com.hp.service.impl;

import com.hp.entity.User;
import com.hp.mapper.UserMapper;
import com.hp.service.IUserServicce;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class UserServiceImpl implements IUserServicce {
@Autowired
private UserMapper userMapper;
@Override
public User login(User user){
User u = userMapper.selectUser(user);
return u;
}

@Override
public void register(User user) {
    userMapper.inserUser(user);
}

package com.hp.controller;

import com.hp.entity.User;
import com.hp.service.IUserServicce;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.servlet.ModelAndView;
@Controller
@RequestMapping("/userController")
public class UserController {
@Autowired
private IUserServicce userServicce;
@RequestMapping(value = {"/login"},method = {RequestMethod.POST})
public String login(@RequestParam("U_NAME") String U_NAME, @RequestParam("U_PS") String U_PS, Model model){
User user = new User();
user.setU_NAME(U_NAME);
user.setU_PS(U_PS);

    if (userServicce.login(user) != null){

        model.addAttribute("U_NAME",U_NAME);
        return "success";
    }
    else {

        model.addAttribute("error","账号或密码错误");
        return "unsuccess";
    }
}

}**

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.hp.mapper.UserMapper">

<select id="selectUser" parameterType="com.hp.entity.User" resultType="com.hp.entity.User">
    select * from t_user
    <where>
        <if test="U_NAME != null and U_NAME !=''">
            and U_NAME = #{U_NAME}
        </if>
        <if test="U_PS != null and U_PS !=''">
            and U_PS = #{U_PS}
        </if>
    </where>
</select>

    <insert id="insertUser" parameterType="com.hp.entity.User">
        insert into t_user(U_NAME,U_PS,U_PHONE)
        values (#{U_NAME},#{U_PS},#{U_PHONE})
    </insert>
</mapper>

可以打印一些信息或者写个单元测试调试下看看是数据的问题还是其他异常导致，如service未加载到内存等，数据库是否有对应的记录，selectUser是否可以查询出数据？