目录

MyBatisPlus是基于MyBatis框架基础上开发的增强型工具，旨在简化开发、提高效率。

1.入门案例

①创建SpringBoot项目，添加Spring Web和Mysql driver

②手动在pom.xml文件中添加mybatis plus和druid依赖

<dependency>
  <groupId>com.baomidou</groupId>
  <artifactId>mybatis-plus-boot-starter</artifactId>
  <version>3.5.3.1</version>
</dependency>
<dependency>
  <groupId>com.alibaba</groupId>
  <artifactId>druid</artifactId>
  <version>1.2.18</version>
</dependency>

 ③创建数据库mybatis，创建User表。

④JDBC配置（application.yml）

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

⑤制作实体类（类名与数据库表名类似，类的属性和表字段对应）

domain.User.java

package com.example.domain;

public class User {
    private long id;
    private int age;
    private String name, password, tel;

    public long getId() {
        return id;
    }

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

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

    public int getAge() {
        return age;
    }

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

    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 String getTel() {
        return tel;
    }

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

⑥定义数据接口，继承BaseMapper

dao.UserDao.java

package com.example.dao;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.example.domain.User;
import org.apache.ibatis.annotations.Mapper;

@Mapper
public interface UserDao extends BaseMapper<User> {
}

⑦测试类测试功能

package com.example;

import com.example.dao.UserDao;
import com.example.domain.User;
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
class MpDemoApplicationTests {

    @Autowired
    private UserDao userDao;

    @Test
    void testGetAll() {
        List<User> userList = userDao.selectList(null);
        System.out.println(userList);

    }
}

2. 标准数据层CRUD开发

测试类

package com.example;

import com.example.dao.UserDao;
import com.example.domain.User;
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
class MpDemoApplicationTests {

    @Autowired
    private UserDao userDao;

    @Test
    void testSave() {
        User user = new User();
        user.setName("鼠鼠");
        user.setPassword("666");
        user.setAge(13);
        user.setTel("88888");
        userDao.insert(user);
    }

    @Test
    void testDelete() {
        userDao.deleteById(4);
    }

    @Test
    void testUpdate() {
        User user = new User();
        user.setId(1L);
        user.setName("Tom88");
        user.setPassword("tom888");
        userDao.updateById(user);
    }

    @Test
    void testGetById() {
        User user = userDao.selectById(2L);
        System.out.println(user);
    }

    @Test
    void testGetAll() {
        List<User> userList = userDao.selectList(null);
        System.out.println(userList);
    }
}

3.Lombok

Lombok，一个Java类库，提供了一组注解，简化POJO实体类的开发。

在pom.xml中添加依赖

<dependency>
  <groupId>org.projectlombok</groupId>
  <artifactId>lombok</artifactId>
</dependency>

domain.User.java

package com.example.domain;

import lombok.Getter;
import lombok.Setter;
import lombok.ToString;

@Setter
@Getter
@ToString
public class User {
    private long id;
    private int age;
    private String name, password, tel;
}

或

package com.example.domain;

import lombok.Data;

@Data
public class User {
    private long id;
    private int age;
    private String name, password, tel;
}

4.分页查询

设置分页拦截器作为Spring管理的bean。

config.Mpconfig.java

package com.example.config;

import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class MpConfig {
    @Bean
    public MybatisPlusInterceptor mpInterceper() {
        // 1. 定义Mp拦截器
        MybatisPlusInterceptor mpInterceptor = new MybatisPlusInterceptor();
        mpInterceptor.addInnerInterceptor(new PaginationInnerInterceptor());
        return mpInterceptor;
    }
}

测试类

@Test
void testGetByPage() {
  IPage page = new Page(1, 2);
  userDao.selectPage(page, null);
  System.out.println("当前页码值：" + page.getCurrent());
  System.out.println("每页显示数：" + page.getSize());
  System.out.println("一共多少页：" + page.getPages());
  System.out.println("一共多少条数据：" + page.getTotal());
  System.out.println("数据：" + page.getRecords());
}