# MyBatis-Plus 简介

MyBatisPlus (简称 MP) 是基于 MyBatis 框架基础上开发的增强型工具，指在简化开发，提高效率
开发方式
- 基于 MyBatis 使用 MyBatisPlus
- 基于 Spring 使用 MyBatisPlus
- 基于 SpringBoot 使用 MyBatisPlus

创建新模块，选择 Spring 初始化，并配置模块相关基础信息

image_2023-03-11-16-59-42

选择当前模块需要使用的技术集 (仅保留 JDBC)

image_2023-03-11-17-00-30

手工添加 MyBatis-Plus 起步依赖

	<dependency>
	<groupId>com.baomidou</groupId>
	<artifactId>mybatis-plus-boot-starter</artifactId>
	<version>3.4.1</version>
	</dependency>

注意事项:

由于 MyBatis-Plus 并未被收录到 idea 的系统内置配置，无法直接选择加入

设置 Jdbc 参数 (application.yml)

	spring:
	datasource:
	type: com.alibaba.druid.pool.DruidDataSource
	driver-class-name: com.mysql.cj.jdbc.Driver
	url: jdbc:mysql://localhost:3306/mybatisplus?characterEncoding=utf-8&serverTimezone=UTC
	username: root
	password: dkx

注意事项:

如果使用 Druid 数据源，需要导入对应坐标

	<dependency>
	<groupId>com.alibaba</groupId>
	<artifactId>druid</artifactId>
	<version>1.2.8</version>
	</dependency>

制作实体类与表结构 (类名与表名对应，属性名与字段名对应，否则查询出错)

	create table plus (
	`id` bigint(20) primary key auto_increment,
	`name` varchar(30) not null,
	`password` varchar(30) not null,
	`age` int(3) not null,
	`tel` varchar(30)
	)character set utf8;

	public class Plus {
	private Long id;
	private String name;
	private String password;
	private Integer age;
	private String tel;

	public Plus(Long id, String name, String password, Integer age, String tel) {
	this.id = id;
	this.name = name;
	this.password = password;
	this.age = age;
	this.tel = tel;
	}

	public Long getId() {
	return id;
	}

	public void setId(Long id) {
	this.id = id;
	}

	public String getName() {
	return name;
	}

	public void setName(String name) {
	this.name = name;
	}

	public String getPassword() {
	return password;
	}

	public void setPassword(String password) {
	this.password = password;
	}

	public Integer getAge() {
	return age;
	}

	public void setAge(Integer age) {
	this.age = age;
	}

	public String getTel() {
	return tel;
	}

	public void setTel(String tel) {
	this.tel = tel;
	}

	@Override
	public String toString() {
	return "User{" +
	"id=" + id +
	", name='" + name + '\'' +
	", password='" + password + '\'' +
	", age=" + age +
	", tel='" + tel + '\'' +
	'}';
	}
	}

定义数据接口，继承 BaseMapper<Plus>

	@Mapper
	public interface UserMapper extends BaseMapper<Plus> {
	}

测试类中注入 dao 接口，测试功能

	@SpringBootTest
	class MavenMybstisplusDemoApplicationTests {
	@Autowired
	private UserMapper userMapper;
	@Test
	void contextLoads() {
	List<Plus> list = userMapper.selectList(null);
	System.out.println(list);
	}
	}
	-------------------------RUN----------------------------
	. ____ _ __ _ _
	/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
	( ( )\___ \| '_ \| '_\| \| '_ \/ _` \| \ \ \ \
	\\/ ___)\| \|_)\| \| \| \| \| \|\| (_\| \| ) ) ) )
	' \|____\| .__\|_\| \|_\|_\| \|_\__, \| / / / /
	=========\|_\|==============\|___/=/_/_/_/
	:: Spring Boot :: (v2.7.9)

	2023-03-11 16:57:06.629 INFO 15900 --- [ main] c.m.MavenMybstisplusDemoApplicationTests : Starting MavenMybstisplusDemoApplicationTests using Java 11.0.16.1 on Administrantor-Dkx with PID 15900 (started by Administrator in E:\apache-maven-3.6.3\maven-work-space\space02\maven-mybstisplus-demo)
	2023-03-11 16:57:06.632 INFO 15900 --- [ main] c.m.MavenMybstisplusDemoApplicationTests : No active profile set, falling back to 1 default profile: "default"
	_ _ \|_ _ _\|_. ___ _ \| _
	\| \| \|\/\|_)(_\| \| \|_\ \|_)\|\|_\|_\
	/ \|
	3.4.1
	2023-03-11 16:57:12.878 INFO 15900 --- [ main] c.m.MavenMybstisplusDemoApplicationTests : Started MavenMybstisplusDemoApplicationTests in 7.705 seconds (JVM running for 11.473)
	2023-03-11 16:57:14.296 INFO 15900 --- [ main] com.alibaba.druid.pool.DruidDataSource : {dataSource-1} inited
	[User{id=1, name='Tom', password='tom', age=3, tel='12987345'}, User{id=2, name='Jerry', password='jerry', age=4, tel='1237568324'}, User{id=3, name='Jock', password='123456', age=41, tel='867862342'}, User{id=4, name='小日子-刘桑', password='it-小日子-刘桑', age=15, tel='912837893759'}]
	2023-03-11 16:57:16.463 INFO 15900 --- [ionShutdownHook] com.alibaba.druid.pool.DruidDataSource : {dataSource-1} closing ...
	2023-03-11 16:57:16.473 INFO 15900 --- [ionShutdownHook] com.alibaba.druid.pool.DruidDataSource : {dataSource-1} closed

	Process finished with exit code 0

# MyBatisPlus 特性

无侵入：只做增强不做改变，不会对现有工程产生影响
强大的 CRUD 操作：内置通用 Mapper, 少量配置即可实现单表 CRUD 操作
支持 Lambda: 编写查询条件无需担心字段写错
支持主键自动生成
内置分页插件
...

# 标准数据层开发

# 标准数据层 CRUD 功能

功能	自定义接口	MP 接口
新增	boolean save(T t)	int insert(T t)
删除	boolean delete(int id)	int deleteById(Serializable id)
修改	boolean update(T t)	int updateById(T t)
根据 id 查询	T getById(int id)	T selectById(Serializable id)
查询全部	List<T> getAll()	List<T> selectList()
分页查询	PageInfo<T> getAll(int page,int size)	IPage<T> selectPage(IPage<T> page)
按条件查询	List<T> getAll(Condition condition)	IPage<T> selectPage(Wrapper<T> queryWrapper)

案例
dao

	@Mapper
	public interface UserMapper extends BaseMapper<Plus> {
	}

domain

	@Data
	public class Plus {
	private Long id;
	private String name;
	private String password;
	private Integer age;
	private String tel;
	}

启动类

[不展示了]

测试代码

	@SpringBootTest
	class MavenMybstisplusDemoApplicationTests {
	@Autowired
	private UserMapper userMapper;

	/**
	* 添加数据
	*/
	@Test
	void insertTest(){
	Plus plus = new Plus();
	plus.setName("大佐-刘桑");
	plus.setPassword("刘桑");
	plus.setAge(123);
	plus.setTel("967487236");
	int i = userMapper.insert(plus);
	String msg = i > 0 ? "执行成功":"执行失败";
	System.out.println(msg);
	}

	/**
	* 通过 id 删除数据
	*/
	@Test
	void deleteTest(){
	int i = userMapper.deleteById(1634506345139843073L);
	String msg = i > 0 ? "执行成功":"执行失败";
	System.out.println(msg);
	}

	/**
	* 通过 id 修改数据
	*/
	@Test
	void updateTest(){
	Plus plus = new Plus();
	plus.setId(1L);
	// plus.setName("Tom666");
	plus.setName("Tom888");
	plus.setPassword("tom888");
	int i = userMapper.updateById(plus);
	String msg = i > 0 ? "执行成功":"执行失败";
	System.out.println(msg);
	}

	/**
	* 通过 id 查询数据
	*/
	@Test
	void selectByIdTest(){
	Plus plus = userMapper.selectById(1L);
	System.out.println(plus);
	}

	/**
	* 查询所有用户信息
	*/
	@Test
	void selectAll() {
	List<Plus> list = userMapper.selectList(null);
	System.out.println(list);
	}
	}
	---------------------RUN---------------------
	. ____ _ __ _ _
	/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
	( ( )\___ \| '_ \| '_\| \| '_ \/ _` \| \ \ \ \
	\\/ ___)\| \|_)\| \| \| \| \| \|\| (_\| \| ) ) ) )
	' \|____\| .__\|_\| \|_\|_\| \|_\__, \| / / / /
	=========\|_\|==============\|___/=/_/_/_/
	:: Spring Boot :: (v2.7.9)

	2023-03-11 20:26:44.900 INFO 10204 --- [ main] c.m.MavenMybstisplusDemoApplicationTests : Starting MavenMybstisplusDemoApplicationTests using Java 11.0.16.1 on Administrantor-Dkx with PID 10204 (started by Administrator in E:\apache-maven-3.6.3\maven-work-space\space02\maven-mybstisplus-demo)
	2023-03-11 20:26:44.902 INFO 10204 --- [ main] c.m.MavenMybstisplusDemoApplicationTests : No active profile set, falling back to 1 default profile: "default"
	_ _ \|_ _ _\|_. ___ _ \| _
	\| \| \|\/\|_)(_\| \| \|_\ \|_)\|\|_\|_\
	/ \|
	3.4.1
	2023-03-11 20:26:50.892 INFO 10204 --- [ main] c.m.MavenMybstisplusDemoApplicationTests : Started MavenMybstisplusDemoApplicationTests in 7.226 seconds (JVM running for 10.072)
	2023-03-11 20:26:52.148 INFO 10204 --- [ main] com.alibaba.druid.pool.DruidDataSource : {dataSource-1} inited
	Plus(id=1, name=Tom888, password=tom888, age=3, tel=12987345)
	[Plus(id=1, name=Tom888, password=tom888, age=3, tel=12987345), Plus(id=2, name=Jerry, password=jerry, age=4, tel=1237568324), Plus(id=3, name=Jock, password=123456, age=41, tel=867862342), Plus(id=4, name=小日子-刘桑, password=it-小日子-刘桑, age=15, tel=912837893759), Plus(id=1634531132654465025, name=大佐-刘桑, password=刘桑, age=123, tel=967487236)]
	执行成功
	执行成功
	执行成功
	2023-03-11 20:26:54.572 INFO 10204 --- [ionShutdownHook] com.alibaba.druid.pool.DruidDataSource : {dataSource-1} closing ...
	2023-03-11 20:26:54.582 INFO 10204 --- [ionShutdownHook] com.alibaba.druid.pool.DruidDataSource : {dataSource-1} closed

	Process finished with exit code 0

# Service CRUD 接口

文档入口：https://baomidou.com/pages/49cc81/#service-crud - 接口

介绍入口：https://blog.csdn.net/qq_44869121/article/details/124297999

说明 ：
通用 Service CRUD 封装 IService 接口，进一步封装 CRUD 采用 get 查询 remove 删除 list 查询集合 page 分页前缀命名方式区分 Mapper 层避免混淆
泛型 T 为任意实体对象
建议如果存在自定义通用 service 方法的可能，请创建自己的 IBaseService 继承 Mybatis-plus 提供的基类
对象 Wrapper 为条件构造器

使用方式：

在 service 接口类中集成 IService <实体类>

	package com.dkx.system.service;

	import com.atguigu.model.system.SysRole;
	import com.baomidou.mybatisplus.extension.service.IService;

	public interface SysRoleService extends IService<SysRole> {
	}

在 serviceImpl 实现类中集成 ServiceImpl 并实现 service 接口类

	package com.dkx.system.service.impl;

	import com.atguigu.model.system.SysRole;
	import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
	import com.dkx.system.mapper.SysRoleMapper;
	import com.dkx.system.service.SysRoleService;
	import org.springframework.stereotype.Service;

	@Service
	public class SysRoleServiceImpl extends ServiceImpl<SysRoleMapper, SysRole> implements SysRoleService {
	}

测试代码：

	package com.dkx.system;

	import com.atguigu.model.system.SysRole;
	import com.dkx.system.service.SysRoleService;
	import org.junit.jupiter.api.Test;
	import org.springframework.beans.factory.annotation.Autowired;
	import org.springframework.boot.test.context.SpringBootTest;

	import java.util.List;

	@SpringBootTest
	public class SysRoleServiceTest {
	@Autowired
	private SysRoleService sysRoleService;
	@Test
	public void testList () {
	List<SysRole> list = sysRoleService.list();
	for (SysRole item : list) {
	System.out.println(item);
	}
	}
	}

结果：

具体里面的一些操作的 CRUD 方法看官方文档。

# MyBatis-Plus 简介

# MyBatisPlus 特性

# 标准数据层开发

# 标准数据层 CRUD 功能

# Service CRUD 接口

MyBatis-ORM

MyBatis-运行报错接口类型不被MapperResitry所知