Java MyBatis-Plus 基本使用

原文：https://mp.baomidou.com/guide/quick-start.html

一、初始化项目

1、新建项目

在idea中，新建Spring Initializr类型的项目。
我这里创建的项目包名是这个：com.example.test5。
然后就是一路next，其它的都不用管。

2、项目新建好后，打开自动导入包

二、添加依赖

1、pom.xml配置

<?xml version="1.0" encoding="UTF-8"?>
<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>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.2.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>test4</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>test4</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <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>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </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>3.3.2</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

2、实际添加的依赖

实际只导入了这三个包：lombok、MyBatis-Plus、mysql

<dependency>
	<groupId>org.projectlombok</groupId>
	<artifactId>lombok</artifactId>
	<optional>true</optional>
</dependency>
<dependency>
	<groupId>com.baomidou</groupId>
	<artifactId>mybatis-plus-boot-starter</artifactId>
	<version>3.3.2</version>
</dependency>
<dependency>
	<groupId>mysql</groupId>
	<artifactId>mysql-connector-java</artifactId>
</dependency>

3、效果如图

三、配置MySQL数据库

1、在resources目录，删掉文件application.properties，新增文件application.yml

# DataSource Config
spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/mybatis?useSSL=false&useUnicode=true&characterEncoding=utf-8&zeroDateTimeBehavior=convertToNull&transformedBitIsBoolean=true&serverTimezone=GMT%2B8
    username: root
    password: root

2、效果如图

四、编码

1、在包entity下，添加类User

1. 在com.example.test5下，新建包entity
   

2. 然后在entity下，添加类User

package com.example.test5.entity;

import lombok.Data;

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

3. 效果如图
   

2、在包'mapper'下，添加类UserMapper

1. 在com.example.test5下，新建包mapper
   

2. 然后在mapper下，添加类UserMapper

package com.example.test5.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.example.test5.entity.User;

public interface UserMapper extends BaseMapper<User> {
}

3、在SpringBoot启动类中，添加@MapperScan注解，扫描`mapper'文件夹

1. 代码如下

package com.example.test5;

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

@SpringBootApplication
@MapperScan("com.example.test5.mapper")
public class Test5Application {

    public static void main(String[] args) {
        SpringApplication.run(Test5Application.class, args);
    }

}

2. 效果如图
   

五、添加测试代码

1、在测试类Test5ApplicationTests中，添加测试代码

1. 代码如下

package com.example.test5;

import com.example.test5.entity.User;
import com.example.test5.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.List;

@SpringBootTest
class Test5ApplicationTests {

    @Autowired
    private UserMapper userMapper;

    @Test
    void contextLoads() {
        System.out.println(("----- selectAll method test ------"));
        List<User> userList = userMapper.selectList(null);
        //Assert.assertEquals(5, userList.size());
        userList.forEach(System.out::println);
    }

}

2. 效果如图
   

六、搭建测试环境

1、创建表

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)
);

2、创建测试数据

DELETE FROM user;

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');

3、效果如图

七、测试

1、先编译一下项目，然后在测试类'Test5ApplicationTests'的'contextLoads'方法上右键，选择Run contextLoads()即可

2、测试结果的查看

八、总结

1、GitHub地址

https://github.com/guxingy/MyBatis-Plus-Example