1. springboot项目基本配置

springboot基本pom依赖

<parent>

    <groupId>org.springframework.boot</groupId>

    <artifactId>spring-boot-starter-parent</artifactId>

    <version>2.5.2</version>

</parent>

<dependencies>

    <dependency>

        <groupId>org.springframework.boot</groupId>

        <artifactId>spring-boot-starter-web</artifactId>

    </dependency>

    <dependency>

        <groupId>org.projectlombok</groupId>

        <artifactId>lombok</artifactId>

        <optional>true</optional>

    </dependency>

</dependencies>

主启动类，此处在 com.hex下建立

package com.hex;

import org.mybatis.spring.annotation.MapperScan;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication

public class MainApplication {

    public static void main(String[] args) {

        SpringApplication.run(MainApplication.class, args);

    }

}

2. mysql准备工作

首先创建一个表

CREATE TABLE `sys_user` (

  `id` BIGINT(20) NOT NULL AUTO_INCREMENT COMMENT '主键',

  `user_name` VARCHAR(64) NOT NULL DEFAULT 'NULL' COMMENT '用户名',

  `nick_name` VARCHAR(64) NOT NULL DEFAULT 'NULL' COMMENT '昵称',

  `password` VARCHAR(64) NOT NULL DEFAULT 'NULL' COMMENT '密码',

  `del_flag` INT(11) DEFAULT '0' COMMENT '删除标志（0代表未删除，1代表已删除）',

  PRIMARY KEY (`id`)

) ENGINE=INNODB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8mb4 COMMENT='用户表'

引入mysql依赖

<!-- 引入mysql依赖-->

<dependency>

    <groupId>mysql</groupId>

    <artifactId>mysql-connector-java</artifactId>

</dependency>

在resources下新建application.yml文件，配置mysql相关信息（按实际自行修改配置）

spring:

  datasource:

    url: jdbc:mysql://localhost:3306/db2022?characterEncoding=utf-8&serverTimezone=UTC

    username: root

    password: 123456

    driver-class-name: com.mysql.cj.jdbc.Driver

3. 使用mybaitsplus

引入依赖

<!-- 引入mybaitsplus依赖-->

<dependency>

    <groupId>com.baomidou</groupId>

    <artifactId>mybatis-plus-boot-starter</artifactId>

    <version>3.4.3</version>

</dependency>

创建user实体类，这里注意2点

1. 在类定义前加注解 @TableName("sys_user")，参数为表名
2. 在主键上添加注解 @TableId

package com.hex.domain;

import com.baomidou.mybatisplus.annotation.TableId;

import com.baomidou.mybatisplus.annotation.TableName;

import lombok.AllArgsConstructor;

import lombok.Data;

import lombok.NoArgsConstructor;

import java.io.Serializable;

import java.util.Date;

/**

 * 用户表(User)实体类

 */

@Data

@AllArgsConstructor

@NoArgsConstructor

@TableName("sys_user")

public class User implements Serializable {

    private static final long serialVersionUID = -40356785423868312L;

    /**

    * 主键

    */

    @TableId

    private Long id;

    /**

    * 用户名

    */

    private String userName;

    /**

    * 昵称

    */

    private String nickName;

    /**

    * 密码

    */

    private String password;

    /**

    * 删除标志（0代表未删除，1代表已删除）

    */

    private Integer delFlag;

}

创建UserMapper类，继承 BaseMapper<T>

package com.hex.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;

import com.hex.domain.User;

public interface UserMapper extends BaseMapper<User> {

}

在主启动类添加扫描mapper注解：@MapperScan("com.hex.mapper")，参数为UserMapper的路径

import org.mybatis.spring.annotation.MapperScan;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication

@MapperScan("com.hex.mapper")

public class MainApplication {

    public static void main(String[] args) {

        SpringApplication.run(MainApplication.class, args);

    }

}

4. 单元测试看效果

引入junit依赖

<!--单元测试-->

<dependency>

    <groupId>org.springframework.boot</groupId>

    <artifactId>spring-boot-starter-test</artifactId>

</dependency>

在test/java/com/hex下，建立测试类 MapperTest，

添加 @SpringBootTest，使用 @Autowired（或者@Resource） 注入userMapper，如下

import com.hex.domain.User;

import com.hex.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

public class MapperTest {

    @Autowired

    public UserMapper userMapper;

    @Test

    public void testUserMapper(){

        List<User> users = userMapper.selectList(null);

        System.out.println(users);

    }

}

结果可在控制台查看用户列表信息输出

2022-02-25 12:40:35.849  INFO 13272 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...

2022-02-25 12:40:38.134  INFO 13272 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.

[User(id=1, userName=hex, nickName=hex, password=123456, delFlag=0)]