Java框架-MybatisPlus入门使用

附上官网，本文基于官网学习

先会用，后分析原理！

本文创建Mysql数据库表（官方使用H2）

DROP TABLE IF EXISTS USER;

CREATE TABLE USER
(
	id BIGINT(20) NOT NULL COMMENT '主键ID',
	NAME VARCHAR(30) NULL DEFAULT NULL COMMENT '姓名',
	age INT(11) NULL DEFAULT NULL COMMENT '年龄',
	email VARCHAR(50) NULL DEFAULT NULL COMMENT '邮箱',
	PRIMARY KEY (id)
);
DELETE FROM USER;

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]');

新建springboot项目，添加依赖至pom.xml

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.2.6.RELEASE</version>
    <relativePath/>
</parent>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.3.1.tmp</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.26</version>
        </dependency>
    </dependencies>

在application.yml中配置数据库连接相关信息（每个人的配置都不同）

# DataSource Config
spring:
  datasource:
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql://localhost:3306/mybatis?useSSL=false&useUnicode=true&characterEncoding=utf-8
    username: root
    password: root

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

package com.example.mybatisplus;

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

@SpringBootApplication
@MapperScan("com.example.mybatisplus.mapper")
public class MybatisplusApplication {

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

}

编写实体类

package com.example.mybatisplus.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
    private Long id;
    private String name;
    private Integer age;
    private String email;
}

编写Mapper类 UserMapper.java，传入泛型自动编写了CRUD操作

package com.example.mybatisplus.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.example.mybatisplus.pojo.User;
import org.springframework.stereotype.Repository;

@Repository
public interface UserMapper extends BaseMapper<User> {
}

测试！

package com.example.mybatisplus;

import com.example.mybatisplus.mapper.UserMapper;
import com.example.mybatisplus.pojo.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 MybatisplusApplicationTests {

    @Autowired
    private UserMapper userMapper;

    @Test
    void contextLoads() {
        //方法来自父类BaseMapper 我们可以自行编写接口增加方法
        //参数是一个条件构造器，null表示无条件
        List<User> users = userMapper.selectList(null);
        users.forEach(System.out::println);
    }

}

总结分析！

使用前我们都需要导入所需的坐标，通过@MapperScan扫描到接口，接口继承了BaseMapper帮我们实现一些简单的通用的mapper，我们只需要传入泛型即可，具体可以通过查看BaseMapper！