mybatis-plus教程--ActiveRecord

冷不防 2023-06-13 08:54 92阅读 0赞

## 完整代码 ##

[https://github.com/pbteach/mybatis-plus-test][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-01]  
[http://www.pbteach.com/post/java\_distribut/mybatis-plus-02/][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 ###

### 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

![1573690631014][]

### 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

![1573690647338][]

### 删除操作 ###

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)

[https_github.com_pbteach_mybatis-plus-test]: https://github.com/pbteach/mybatis-plus-test
[http_www.pbteach.com_post_java_distribut_mybatis-plus-01]: http://www.pbteach.com/post/java_distribut/mybatis-plus-01/
[http_www.pbteach.com_post_java_distribut_mybatis-plus-02]: http://www.pbteach.com/post/java_distribut/mybatis-plus-02/
[1573690631014]: https://imgconvert.csdnimg.cn/aHR0cDovL3d3dy5wYnRlYWNoLmNvbS9wb3N0L2phdmFfZGlzdHJpYnV0L215YmF0aXMtcGx1cy0wMi8xNTczNjkwNjMxMDE0LnBuZw?x-oss-process=image/format,png
[1573690647338]: https://imgconvert.csdnimg.cn/aHR0cDovL3d3dy5wYnRlYWNoLmNvbS9wb3N0L2phdmFfZGlzdHJpYnV0L215YmF0aXMtcGx1cy0wMi8xNTczNjkwNjQ3MzM4LnBuZw?x-oss-process=image/format,png