Mybatis plus无介绍快使用，CRUD增删改查基本使用附源码（一）

问题背景

因为mybatis plus非常的流行，虽然平常mybatis generator也够用了，但多会一个，看别人的代码就轻松一点
注意事项：

• 官方网站：https://baomidou.com/
• 官方文档：https://baomidou.com/pages/24112f/
• 可以自己创建工程，也可以下载源码进行参考
• 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，实体类entity属性都使用对象，使用Long，不能使用long，不然雪花算法会失效
  

建库建表

1 打开Navicat运行以下SQL脚本进行建库建表

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;

2 插入几条测试数据

INSERT INTO user (id, name, age, email) VALUES 
(1, 'Jone', 18, '[email protected]'), 
(2, 'Jack', 20, '[email protected]'), 
(3, 'Tom', 28, '[email protected]'), 
(4, 'Sandy', 21, '[email protected]'), 
(5, 'Billie', 24, '[email protected]');

项目创建

1 引入pom依赖

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0modelVersion>
    <parent>
        <groupId>org.springframework.bootgroupId>
        <artifactId>spring-boot-starter-parentartifactId>
        <version>2.6.8version>
        <relativePath/> 
    parent>
    <groupId>com.yggroupId>
    <artifactId>mybatis-plusartifactId>
    <version>0.0.1-SNAPSHOTversion>
    <name>mybatis-plusname>
    <description>Demo project for Spring Bootdescription>
    <properties>
        <java.version>1.8java.version>
    properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-webartifactId>
        dependency>

        <dependency>
            <groupId>org.projectlombokgroupId>
            <artifactId>lombokartifactId>
            <optional>trueoptional>
        dependency>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-testartifactId>
        
        dependency>
        
        <dependency>
            <groupId>com.baomidougroupId>
            <artifactId>mybatis-plus-boot-starterartifactId>
            <version>3.5.1version>
        dependency>
        <dependency>
            <groupId>mysqlgroupId>
            <artifactId>mysql-connector-javaartifactId>
            <scope>runtimescope>
        dependency>
    dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.bootgroupId>
                <artifactId>spring-boot-maven-pluginartifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombokgroupId>
                            <artifactId>lombokartifactId>
                        exclude>
                    excludes>
                configuration>
            plugin>
        plugins>
    build>

project>

2 使用IDEA连接数据库

3 右键user选择Scripted Extensions→Generate POJOs.groovy生成数据库user实体类
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4 删除set和get，添加@Data注解

package com.yg.mybatisplus.entity;


import lombok.Data;

@Data
public class User {

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

}

5 创建mapper接口，集成com.baomidou.mybatisplus.core.mapper.BaseMapper可以使用增删改查方法

package com.yg.mybatisplus.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.yg.mybatisplus.entity.User;
import org.springframework.stereotype.Repository;

/**
 * @Author suolong
 * @Date 2022/6/2 17:25
 * @Version 2.0
 */
@Repository
public interface UserMapper extends BaseMapper<User> {

}

6 application.yml配置

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://xxx/database?severTimezone=Asia/Shanghai&allowMultiQueries=true&autoReconnect=true&characterEncoding=UTF-8&useUnicode=true&useSSL=false
    username: xxx
    password: 123456

#生成sql日志打印，一般关闭
mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

7 启动类

package com.yg.mybatisplus;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@MapperScan("com.yg.mybatisplus.mapper") //扫描所有的mapper
@SpringBootApplication
public class MybatisPlusApplication {

    public static void main(String[] args) {
        SpringApplication.run(MybatisPlusApplication.class, args);
    }

}

8 测试CRUD增删改查

package com.yg.mybatisplus;

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

import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * @Author suolong
 * @Date 2022/6/2 17:42
 * @Version 2.0
 */

@SpringBootTest
public class MybatisPlusTest {

    @Autowired
    UserMapper userMapper;


    @Test
    void selectTest(){
        //全查
        List<User> users = userMapper.selectList(null);
        users.forEach(System.out::println);
    }

    /**
     * 测试插入一条数据
     * 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
     */
    @Test
    public void testInsert(){
        User user = new User();
        user.setName("Vz1");
        user.setAge(211);
        user.setEmail("[email protected]");
        int result = userMapper.insert(user);
        System.out.println(result > 0 ? "添加成功！" : "添加失败！");
        System.out.println("受影响的行数为：" + result);
        //1527206783590903810（当前 id 为雪花算法自动生成的id）
        System.out.println("id自动获取" + user.getId());
    }

    /**
     * 测试根据id删除一条数据
     */
    @Test
    public void testDeleteById(){
        int result = userMapper.deleteById(1533011356262625282L);
        System.out.println(result > 0 ? "删除成功！" : "删除失败！");
        System.out.println("受影响的行数为：" + result);
    }

    /**
     * 测试通过id批量删除数据
     */
    @Test
    public void testDeleteBatchIds(){
        List<Long> ids = Arrays.asList(1532349895093833729L,1533012537454157826L,1533012657583161345L);
        int result = userMapper.deleteBatchIds(ids);
        System.out.println(result > 0 ? "删除成功！" : "删除失败！");
        System.out.println("受影响的行数为：" + result);
    }

    /**
     * 测试根据Map集合中所设置的条件删除数据
     */
    @Test
    public void testDeleteByMap(){
        //当前演示为根据name和age删除数据
        //执行SQL为：DELETE FROM user WHERE name = ? AND age = ?
        Map<String,Object> map = new HashMap<>();
        map.put("name","Vz1 ");
        map.put("age",211);
        int result = userMapper.deleteByMap(map);
        System.out.println(result > 0 ? "删除成功！" : "删除失败！");
        System.out.println("受影响的行数为：" + result);
    }

    /**
     * 测试根据id修改用户信息, 只修改改变的值, 其他信息保持原值
     */
    @Test
    public void testUpdateById(){
        //执行SQL为： UPDATE user SET name=?, age=?, email=? WHERE id=?
        User user = new User();
        user.setId(5L);
        user.setEmail("[email protected]");
        int result = userMapper.updateById(user);
        System.out.println(result > 0 ? "修改成功！" : "修改失败！");
        System.out.println("受影响的行数为：" + result);
    }

    /**
     * 测试根据id查询用户数据
     */
    @Test
    public void testSelectById(){
        User user = userMapper.selectById(1L);
        System.out.println(user);
    }

    /**
     * 根据多个id查询用户数据
     */
    @Test
    public void testSelectBatchIds(){
        //执行SQL为：SELECT id,name,age,email FROM user WHERE id IN ( ? , ? , ? )
        List<Long> ids = Arrays.asList(1L,2L,3L);
        List<User> users = userMapper.selectBatchIds(ids);
        users.forEach(System.out::println);
    }

    /**
     * 根据Map所设置的条件查询用户
     */
    @Test
    public void testSelectByMap(){
        //执行SQL为：SELECT id,name,age,email FROM user WHERE age = ?
        Map<String,Object> map = new HashMap<>();
        map.put("age",18);
        List<User> users = userMapper.selectByMap(map);
        users.forEach(System.out::println);
    }

}

9 项目目录

总结

快使用就是查看CRUD增删改查怎么用的

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