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：

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

<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>4.0.0modelVersion>

    <parent>
        <groupId>org.springframework.bootgroupId>
        <artifactId>spring-boot-starter-parentartifactId>
        <version>3.0.5version>
    parent>
    <groupId>com.sunsplantergroupId>
    <artifactId>Spring-With-MybatisPlusartifactId>
    <version>1.0-SNAPSHOTversion>

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


    <dependencies>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starterartifactId>
        dependency>
        
        
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-testartifactId>
        dependency>
        
        
        <dependency>
            <groupId>com.baomidougroupId>
            <artifactId>mybatis-plus-boot-starterartifactId>
            <version>3.5.3.1version>
        dependency>

        
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-jdbcartifactId>
        dependency>

        
        <dependency>
            <groupId>com.alibabagroupId>
            <artifactId>druid-spring-boot-3-starterartifactId>
            <version>1.2.20version>
        dependency>

        
        <dependency>
            <groupId>mysqlgroupId>
            <artifactId>mysql-connector-javaartifactId>
            <version>8.0.28version>
        dependency>

        <dependency>
            <groupId>org.projectlombokgroupId>
            <artifactId>lombokartifactId>
            <version>1.18.28version>
        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 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);
    }
}