完整代码

https://github.com/pbteach/mybatis-plus-test

完整讲义

http://www.pbteach.com/post/java_distribut/mybatis-plus-01/
http://www.pbteach.com/post/java_distribut/mybatis-plus-02/

准备环境

创建数据库和表：

-- 创建测试表
CREATE TABLE `tb_user` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '主键ID',
  `user_name` varchar(20) NOT NULL COMMENT '用户名',
  `password` varchar(20) NOT NULL COMMENT '密码',
  `name` varchar(30) DEFAULT NULL COMMENT '姓名',
  `age` int(11) DEFAULT NULL COMMENT '年龄',
  `email` varchar(50) DEFAULT NULL COMMENT '邮箱',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

-- 插入测试数据
INSERT INTO `tb_user` (`id`, `user_name`, `password`, `name`, `age`, `email`) VALUES ('1', 'zhangsan', '123456', '张三', '18', 'test1@pbteach.com');
INSERT INTO `tb_user` (`id`, `user_name`, `password`, `name`, `age`, `email`) VALUES ('2', 'lisi', '123456', '李四', '20', 'test2@pbteach.com');
INSERT INTO `tb_user` (`id`, `user_name`, `password`, `name`, `age`, `email`) VALUES ('3', 'wangwu', '123456', '王五', '28', 'test3@pbteach.com');
INSERT INTO `tb_user` (`id`, `user_name`, `password`, `name`, `age`, `email`) VALUES ('4', 'zhaoliu', '123456', '赵六', '21', 'test4@pbteach.com');
INSERT INTO `tb_user` (`id`, `user_name`, `password`, `name`, `age`, `email`) VALUES ('5', 'sunqi', '123456', '孙七', '24', 'test5@pbteach.com');

ActiveRecord

ActiveRecord（简称AR）一直广受动态语言（ PHP 、 Ruby 等）的喜爱，而 Java 作为准静态语言，对于 ActiveRecord 往往只能感叹其优雅，所以我们也在 AR 道路上进行了一定的探索，喜欢大家能够喜欢。

什么是ActiveRecord？

ActiveRecord也属于ORM（对象关系映射）层，由Rails最早提出，遵循标准的ORM模型：表映射到记录，记录映射到对象，字段映射到对象属性。配合遵循的命名和配置惯例，能够很大程度的快速实现模型的操作，而且简洁易懂。

ActiveRecord的主要思想是：

• 每一个数据库表对应创建一个类，类的每一个对象实例对应于数据库中表的一行记录；通常表的每个字段在类中都有相应的Field；
• ActiveRecord同时负责把自己持久化，在ActiveRecord中封装了对数据库的访问，即CURD;；
• ActiveRecord是一种领域模型(Domain Model)，封装了部分业务逻辑；

开启AR之旅

在MP中，开启AR非常简单，只需要将实体对象继承Model即可。

package com.pbteach.mp.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 com.baomidou.mybatisplus.extension.activerecord.Model;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class User extends Model<User> {

    private Long id;
    private String userName;
    private String password;
    private String name;
    private Integer age;
    private String email;

}

根据主键查询

@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {

    @Autowired
    private UserMapper userMapper;

    @Test
    public void testAR() {
        User user = new User();
        user.setId(2L);
        User user2 = user.selectById();

        System.out.println(user2);
    }

}

新增数据

@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {

    @Autowired
    private UserMapper userMapper;

    @Test
    public void testAR() {
        User user = new User();
        user.setName("刘备");
        user.setAge(30);
        user.setPassword("123456");
        user.setUserName("liubei");
        user.setEmail("liubei@pbteach.com");

        boolean insert = user.insert();

        System.out.println(insert);
    }

}

结果：

[main] [com.pbteach.mp.mapper.UserMapper.insert]-[DEBUG] ==>  Preparing: INSERT INTO tb_user ( user_name, password, name, age, email ) VALUES ( ?, ?, ?, ?, ? ) 
[main] [com.pbteach.mp.mapper.UserMapper.insert]-[DEBUG] ==> Parameters: liubei(String), 123456(String), 刘备(String), 30(Integer), liubei@pbteach.com(String)
[main] [com.pbteach.mp.mapper.UserMapper.insert]-[DEBUG] <==    Updates: 1

更新操作

@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {

    @Autowired
    private UserMapper userMapper;

    @Test
    public void testAR() {
        User user = new User();
        user.setId(8L);
        user.setAge(35);

        boolean update = user.updateById();
        System.out.println(update);
    }

}

结果：

[main] [com.pbteach.mp.mapper.UserMapper.updateById]-[DEBUG] ==>  Preparing: UPDATE tb_user SET age=? WHERE id=? 
[main] [com.pbteach.mp.mapper.UserMapper.updateById]-[DEBUG] ==> Parameters: 35(Integer), 8(Long)
[main] [com.pbteach.mp.mapper.UserMapper.updateById]-[DEBUG] <==    Updates: 1

删除操作

@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {

    @Autowired
    private UserMapper userMapper;

    @Test
    public void testAR() {
        User user = new User();
        user.setId(7L);

        boolean delete = user.deleteById();
        System.out.println(delete);
    }

}

结果：

[main] [com.pbteach.mp.mapper.UserMapper.deleteById]-[DEBUG] ==>  Preparing: DELETE FROM tb_user WHERE id=? 
[main] [com.pbteach.mp.mapper.UserMapper.deleteById]-[DEBUG] ==> Parameters: 7(Long)
[main] [com.pbteach.mp.mapper.UserMapper.deleteById]-[DEBUG] <==    Updates: 1

根据条件查询

@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {

    @Autowired
    private UserMapper userMapper;

    @Test
    public void testAR() {
        User user = new User();
        QueryWrapper<User> userQueryWrapper = new QueryWrapper<>();
        userQueryWrapper.le("age","20");

        List<User> users = user.selectList(userQueryWrapper);
        for (User user1 : users) {
            System.out.println(user1);
        }
    }

}

结果：

[main] [com.pbteach.mp.mapper.UserMapper.selectList]-[DEBUG] ==>  Preparing: SELECT id,user_name,password,name,age,email FROM tb_user WHERE age <= ? 
[main] [com.pbteach.mp.mapper.UserMapper.selectList]-[DEBUG] ==> Parameters: 20(String)
[main] [com.pbteach.mp.mapper.UserMapper.selectList]-[DEBUG] <==      Total: 2

User(id=2, userName=lisi, password=123456, name=李四, age=20, email=test2@pbteach.com, address=null)
User(id=6, userName=caocao, password=123456, name=曹操, age=20, email=test@pbteach.com, address=null)

pper.selectList]-[DEBUG] <== Total: 2

User(id=2, userName=lisi, password=123456, name=李四, age=20, email=test2@pbteach.com, address=null)
User(id=6, userName=caocao, password=123456, name=曹操, age=20, email=test@pbteach.com, address=null)