1.MyBatis-Plus-入门案例

1.数据准备

创建数据库表

CREATE DATABASE `mybatis_plus` /*!40100 DEFAULT CHARACTER SET utf8mb4 */;
use `mybatis_plus`;
CREATE TABLE `user` (
    `id` bigint(20) NOT NULL COMMENT '主键ID',
    `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 DEFAULT CHARSET=utf8;.com',0,35);

添加数据

INSERT INTO user (id, name, age, email) VALUES
(1, 'Jone', 18, 'test1@baomidou.com'),
(2, 'Jack', 20, 'test2@baomidou.com'),
(3, 'Tom', 28, 'test3@baomidou.com'),
(4, 'Sandy', 21, 'test4@baomidou.com'),
(5, 'Billie', 24, 'test5@baomidou.com');

创建springboot项目引入依赖

<dependencies>
    <!--web依赖-->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <!--test测试依赖-->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>com.baomidou</groupId>
        <artifactId>mybatis-plus-boot-starter</artifactId>
        <version>3.5.1</version>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <scope>runtime</scope>
    </dependency>
</dependencies>

配置application.yml

server:
  port: 8088
spring:
  datasource:
    type: com.zaxxer.hikari.HikariDataSource
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/mybatis_plus?serverTimezone=GMT%2B8&characterEncoding=utf-8&useSSL=false
    username: root
    password: 1234

实体类（成员变量使用包装类定义，因为普通类型有默认值，影响非空判断）

package com.oracle.pojo;

import lombok.Data;

@Data //lombok注解
public class User {

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

}

添加mapper

public interface UserMapper extends BaseMapper<User> {

}

测试

package com.oracle;

import com.oracle.mapper.UserMapper;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

@SpringBootTest
public class MybatisPlusTest {

    @Autowired
    private UserMapper userMapper;

    @Test
    public void testSelectList(){
        //selectList()根据MP内置的条件构造器查询一个list集合，null表示没有条件，即查询所有
        userMapper.selectList(null).forEach(System.out::println);
    }

}

添加日志

# 配置MyBatis日志
mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

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2.基本CRUD

1.插入

    @Test
    public void testInsert(){
        User user = new User(null, "张三", 23, "zhangsan@atguigu.com");
        //INSERT INTO user ( id, name, age, email ) VALUES ( ?, ?, ?, ? )
        int result = userMapper.insert(user);
        System.out.println("受影响行数："+result);
        //2028791277338980354
        System.out.println("id自动获取："+user.getId());
    }

最终执行的结果，所获取的id为1761203470926962690

这是因为MyBatis-Plus在实现插入数据时，会默认基于雪花算法的策略生成id

2.删除

根据id删除记录

    @Test
    public void testDeleteById(){
        // 通过id删除用户信息
        // DELETE FROM user WHERE id=?
        int result = userMapper.deleteById(2028791277338980354L);
        System.out.println("受影响行数："+result);
    }

根据id批量删除记录

@Test
public void testDeleteBatchIds(){
    //通过多个id批量删除
    //DELETE FROM user WHERE id IN ( ? , ? , ? )
    List<Long> idList = Arrays.asList(1L, 2L, 3L);
    int result = userMapper.deleteBatchIds(idList);
    System.out.println("受影响行数："+result);
}

根据map条件删除

@Test
public void testDeleteByMap(){
    // 根据map集合中所设置的条件删除记录
    // DELETE FROM user WHERE name = ? AND age = ?
    Map<String, Object> map = new HashMap<>();
    map.put("age", 23);
    map.put("name", "张三");
    int result = userMapper.deleteByMap(map);
    System.out.println("受影响行数："+result);
}

3.修改

@Test
public void testUpdateById(){
    User user = new User(4L, "admin", 22, null);
    //UPDATE user SET name=?, age=? WHERE id=?
    int result = userMapper.updateById(user);
    System.out.println("受影响行数："+result);
}

4.查询

根据id查询用户信息

@Test
public void testSelectById(){
    //根据id查询用户信息
    //SELECT id,name,age,email FROM user WHERE id=?
    User user = userMapper.selectById(4L);
    System.out.println(user);
}

根据id查询多个用户信息

@Test
public void testSelectBatchIds(){
    //根据多个id查询多个用户信息
    //SELECT id,name,age,email FROM user WHERE id IN ( ? , ? )
    List<Long> idList = Arrays.asList(4L, 5L);
    List<User> list = userMapper.selectBatchIds(idList);
    list.forEach(System.out::println);
}

根据map条件查询

@Test
public void testSelectByMap(){
    //通过map条件查询用户信息
    //SELECT id,name,age,email FROM user WHERE name = ? AND age = ?
    Map<String, Object> map = new HashMap<>();
    map.put("age", 22);
    map.put("name", "admin");
    List<User> list = userMapper.selectByMap(map);
    list.forEach(System.out::println);
}

5、自定义功能

定义在resource/mapper下即可，这是mp定义的映射文件路径

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3.Service

前缀命名方式区分 Mapper 层与Service层

操作	service	mapper
查询	get/list	select
修改	update	update
删除	remove	delete
增加	save	insert
分页	page	selectPage

1、IService

MyBatis-Plus中有一个接口 IService和其实现类 ServiceImpl，封装了常见的业务层逻辑

详情查看源码IService和ServiceImpl

2、创建Service接口和实现类

/**
 * UserService继承IService模板提供的基础功能
 */
public interface UserService extends IService<User> {

}

package com.oracle.service.impl;

import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.oracle.mapper.UserMapper;
import com.oracle.pojo.User;
import com.oracle.service.UserService;
import org.springframework.stereotype.Service;

/**
 * ServiceImpl实现了IService，提供了IService中基础功能的实现
 * 若ServiceImpl无法满足业务需求，则可以使用自定的UserService定义方法，并在实现类中实现
 */
@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {

}

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