MybatisPlus使用@TableId主键id自增长无效的解决

package com.tong.pojo;

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@NoArgsConstructor
@AllArgsConstructor
@TableName("tb_user")
public class User {
    @TableId(type = IdType.AUTO) //指定id类型为自增长
    private Long id;
    private String user_name;
    private String password;
    private String name;
    private Integer age;
    private String email;

}

package org.example;

import com.tong.MyApplication;
import com.tong.mapper.UserMapper;
import com.tong.pojo.User;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest(classes= MyApplication.class)
public class TestUserMapper {
    @Autowired
    private UserMapper userMapper;
    上面这一行报错是正常现象

    @Test
    public void test(){
        User user = new User();

        user.setEmail("12345.com");
        user.setAge(20);
        user.setUser_name("caocao1");
        user.setName("曹操1");
        user.setPassword("123456");
        //user.setAddress("北京");


        int insert = userMapper.insert(user);
        System.out.println(insert);
        System.out.println(user.getId());
    }
}