mybatis-plus入门

1、快速开始

1.1、现有一张 User 表，其表结构如下

idnameageemali1Jone18test1@baomidou.com2Jack20test2@baomidou.com3Tom28test3@baomidou.com4Sandy21test4@baomidou.com5Billie24test5@baomidou.com

• SQL语句
  

1. DROP TABLE IF EXISTS user;
3. CREATE TABLE `user` (
4.   `id` bigint NOT NULL AUTO_INCREMENT COMMENT '主键ID',
5.   `name` varchar(30) DEFAULT NULL COMMENT '姓名',
6.   `age` int DEFAULT NULL COMMENT '年龄',
7.   `email` varchar(50) DEFAULT NULL COMMENT '邮箱',
8.   `is_deleted` int NOT NULL DEFAULT '0' COMMENT '逻辑删除',
9.   PRIMARY KEY (`id`)
10. ) ENGINE=InnoDB AUTO_INCREMENT=0 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;
12. DELETE FROM user;
14. INSERT INTO user (id, name, age, email,is_deleted) VALUES
15. (1, 'Jone', 18, 'test1@baomidou.com',0),
16. (2, 'Jack', 20, 'test2@baomidou.com',0),
17. (3, 'Tom', 28, 'test3@baomidou.com',0),
18. (4, 'Sandy', 21, 'test4@baomidou.com',0),
19. (5, 'Billie', 24, 'test5@baomidou.com',0);

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1.2、引入依赖

• mybatis-plus-boot-starter
  

1.        <dependency>
2.             <groupId>org.springframework.boot</groupId>
3.             <artifactId>spring-boot-starter-web</artifactId>
4.         </dependency>
5.         <dependency>
6.             <groupId>com.baomidou</groupId>
7.             <artifactId>mybatis-plus-boot-starter</artifactId>
8.             <version>3.5.2</version>
9.         </dependency>
10.         <dependency>
11.             <groupId>mysql</groupId>
12.             <artifactId>mysql-connector-java</artifactId>
13.             <scope>runtime</scope>
14.         </dependency>
15.         <dependency>
16.             <groupId>com.alibaba</groupId>
17.             <artifactId>druid-spring-boot-starter</artifactId>
18.             <version>1.2.11</version>
19.         </dependency>
20.         <dependency>
21.             <groupId>org.springframework.boot</groupId>
22.             <artifactId>spring-boot-starter-test</artifactId>
23.             <scope>test</scope>
24.         </dependency>
25.         <dependency>
26.             <groupId>junit</groupId>
27.             <artifactId>junit</artifactId>
28.             <scope>test</scope>
29.         </dependency>

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1.3、配置数据库连接，开启控制台SQL语句输出

1. spring:
2.   datasource:
3.     type: com.alibaba.druid.pool.DruidDataSource
4.     driver-class-name: com.mysql.cj.jdbc.Driver
5.     url: jdbc:mysql://114.67.111.175:3306/test
6.     username: wq
7.     password: 123456
8. #开启控制台日志
9. mybatis-plus:
10.   configuration:
11.     #控制台打印sql语句方便调试sql语句执行错误
12.     log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
13.     #这个不在控制台打印查询结果,但是在log4j2中打印
14.     #log-impl: org.apache.ibatis.logging.log4j2.Log4j2Impl

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• 在 Spring Boot 启动类中添加 @MapperScan 注解，扫描 Mapper 文件夹：
  

1. @SpringBootApplication
2. @MapperScan("com.wanqi.mybatisplus.mapper")
3. public class Application {
5.     public static void main(String[] args) {
6.         SpringApplication.run(Application.class, args);
7.     }
9. }

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1.4、编码

• 实体类User
  

1. package com.wanqi.mybatisplus.pojo;
4. import com.baomidou.mybatisplus.annotation.IdType;
5. import com.baomidou.mybatisplus.annotation.TableId;
7. @TableName("user") //指定表名
8. public class User {
9.     //type = IdType.AUTO自增字段需要修改数据库主键为自增
10.     //value指定对应主键字段名，type指定id生成策略（默认策略为雪花算法）
11.     @TableId(value = "id", type = IdType.AUTO)
12.     private Long id;
13.     //value数据库字段值
14.     @TableField(value = "name")
15.     private String name;
16.     private Integer age;
17.     private String email;
18.     private Integer isDeleted;
21.     public User(Long id, String name, Integer age, String email) {
22.         this.id = id;
23.         this.name = name;
24.         this.age = age;
25.         this.email = email;
26.     }
27.     public User(String name, Integer age, String email) {
28.         this.name = name;
29.         this.age = age;
30.         this.email = email;
31.     }
33.     public User() {
34.     }
36.     public Long getId() {
37.         return id;
38.     }
40.     public void setId(Long id) {
41.         this.id = id;
42.     }
44.     public String getName() {
45.         return name;
46.     }
48.     public void setName(String name) {
49.         this.name = name;
50.     }
52.     public Integer getAge() {
53.         return age;
54.     }
56.     public void setAge(Integer age) {
57.         this.age = age;
58.     }
60.     public String getEmail() {
61.         return email;
62.     }
64.     public void setEmail(String email) {
65.         this.email = email;
66.     }
68.    public Integer getIsDeleted() {
69.         return isDeleted;
70.     }
72.     public void setIsDeleted(Integer isDeleted) {
73.         this.isDeleted = isDeleted;
74.     }
76.     @Override
77.     public String toString() {
78.         return "User{" +
79.                 "id=" + id +
80.                 ", name='" + name + '\'' +
81.                 ", age=" + age +
82.                 ", email='" + email + '\'' +
83.                 ", isDeleted=" + isDeleted +
84.                 '}';
85.     }
86. }

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• 编写 Mapper 包下的 UserMapper接口
  

1. import com.wanqi.mybatisplus.pojo.User;
2. import org.springframework.stereotype.Repository;
4. @Repository
5. public interface UserMapper extends BaseMapper<User> {
7. }

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1.5、测试使用

1. package com.wanqi.mybatisplus;
3. import com.wanqi.mybatisplus.mapper.UserMapper;
4. import com.wanqi.mybatisplus.pojo.User;
5. import org.junit.jupiter.api.Test;
6. import org.springframework.beans.factory.annotation.Autowired;
7. import org.springframework.boot.test.context.SpringBootTest;
9. import java.util.ArrayList;
10. import java.util.Collection;
11. import java.util.List;
13. @SpringBootTest
14. class MybatisPlusApplicationTests {
16.     @Autowired
17.     private UserMapper userMapper;
19.     @Test
20.     public void testSelect() {
21.         System.out.println(("----- selectAll method test ------"));
22.         userMapper.insert(new User( "古力娜扎", 18, "test1@baomidou.com"));
24.         List<User> userList = userMapper.selectList(null);
25.         userList.forEach(System.out::println);
26.     }
27. }

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2、批量操作

2.1、增加Service 层代码

1. package com.wanqi.mybatisplus.service;
3. import com.baomidou.mybatisplus.extension.service.IService;
4. import com.wanqi.mybatisplus.pojo.User;
6. /**
7. * @Description TODO
8. * @Version 1.0.0
9. * @Date 2022/9/1
10. * @Author wandaren
11. */
12. public interface UserService extends IService<User> {
13. }

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• 注意 UserServiceImpl 必须要继承 MP 框架中的 ServiceImpl，不然要重写很多方法。
  

1. package com.wanqi.mybatisplus.service;
3. import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
4. import com.wanqi.mybatisplus.mapper.UserMapper;
5. import com.wanqi.mybatisplus.pojo.User;
6. import org.springframework.stereotype.Service;
8. /**
9. * @Description TODO
10. * @Version 1.0.0
11. * @Date 2022/9/1
12. * @Author wandaren
13. */
14. @Service
15. public class UserServiceImpl extends ServiceImpl<UserMapper, User>
16.     implements UserService{
17. }

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2.2、测试使用

1. package com.wanqi.mybatisplus;
3. import com.wanqi.mybatisplus.mapper.UserMapper;
4. import com.wanqi.mybatisplus.pojo.User;
5. import com.wanqi.mybatisplus.service.UserServiceImpl;
6. import org.junit.jupiter.api.Test;
7. import org.springframework.beans.factory.annotation.Autowired;
8. import org.springframework.boot.test.context.SpringBootTest;
10. import java.util.ArrayList;
11. import java.util.Collection;
12. import java.util.List;
14. @SpringBootTest
16. class MybatisPlusApplicationTests {
17.     @Autowired
18.     private UserServiceImpl userService;
20.     @Test
21.     void contextLoads() {
22.         Collection<User> userList = new ArrayList<>();
23.         userList.add(new User("hhh", 18, "test1@baomidou.com"));
24.         userList.add(new User("sss", 18, "test1@baomidou.com"));
25.         userList.add(new User("ddd", 18, "test1@baomidou.com"));
26.         userService.saveBatch(userList);
27.         System.out.println(userService.list());
28.     }
29. }

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3、Service CURD

3.1、save

1. // 插入一条记录（选择字段，策略插入）
2. boolean save(T entity);
3. // 插入（批量）
4. boolean saveBatch(Collection<T> entityList);
5. // 插入（批量）
6. boolean saveBatch(Collection<T> entityList, int batchSize);

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3.2、saveOrUpdate

1. // TableId 注解存在更新记录，否插入一条记录
2. boolean saveOrUpdate(T entity);
3. // 根据updateWrapper尝试更新，否继续执行saveOrUpdate(T)方法
4. boolean saveOrUpdate(T entity, Wrapper<T> updateWrapper);
5. // 批量修改插入
6. boolean saveOrUpdateBatch(Collection<T> entityList);
7. // 批量修改插入
8. boolean saveOrUpdateBatch(Collection<T> entityList, int batchSize);

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3.3、remove

[code]// 根据 entity 条件，删除记录boolean remove(Wrapper queryWrapper);// 根据 ID 删除boolean removeById(Serializable id);// 根据 columnMap 条件，删除记录boolean removeByMap(Map columnMap);// 删除（根据ID 批量删除）boolean removeByIds(Collection