01 MyBatisPlus快速入门

1. MyBatis-Plus快速入门

版本 3.5.31
并非另起炉灶 , 而是MyBatis的增强 , 使用之前依然要导入MyBatis的依赖 , 且之前MyBatis的所有功能依然可以使用.
局限性是仅限于单表操作, 对于多表仍需要手写

项目结构：
在这里插入图片描述

先导入依赖，比之前多了一个mybatis-plus-boot-starter

<?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 http://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>3.0.5</version>
    </parent>
    <groupId>com.sunsplanter</groupId>
    <artifactId>Spring-With-MybatisPlus</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>17</maven.compiler.source>
        <maven.compiler.target>17</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>


    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        
        <!-- 测试环境 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
        </dependency>
        
        <!-- mybatis-plus  -->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.5.3.1</version>
        </dependency>

        <!-- 数据库相关配置启动器 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>

        <!-- druid启动器的依赖  -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid-spring-boot-3-starter</artifactId>
            <version>1.2.20</version>
        </dependency>

        <!-- 驱动类-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.28</version>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.28</version>
        </dependency>

    </dependencies>

连接池配置：

# 连接池配置
spring:
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    druid:
      url: jdbc:mysql://localhost:3306/carreseller
      username: root
      password: ？？？
      driver-class-name: com.mysql.cj.jdbc.Driver

实体类：

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

mapper接口：

package com.sunsplanter.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.sunsplanter.pojo.User;

//
public interface UserMapper extends BaseMapper<User> {
    //之前，mapper接口内要声明抽象方法，然后再mapper.xml中具体写查询语句
    //List<User> queryAll();

    //现在，继承自BaseMapper，其内已定义了几乎所有单表查询语句
    //故UserMapper也拥有了这些方法，无需再写
}

采用测试类的方法，不需要定义main方法启动类

package com.sunsplanter.test;

import com.sunsplanter.mapper.UserMapper;
import com.sunsplanter.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;

//SpringBoot的专有测试注解，可以帮我们自动初始化IoC容器，想要什么直接拿即可
@SpringBootTest
public class SpringWithMyBatisPlusTest {
    @Autowired
    private UserMapper userMapper;

    //加Test注解，为了能执行单个测试方法
    @Test
    public void test(){
        //该方法查询全部
        //参数是一个Wrapper，条件结构器，这里先不用 填null
        List<User> user = userMapper.selectList(null);

        System.out.println(user);
    }
}