[MyBatisPlus implements super detailed file upload and download....]

1. database settings

CREATE DATABASE IMAGETEST;
USE IMAGETEST;
CREATE TABLE `photo` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `images` varchar(100) COLLATE utf8_czech_ci DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8 COLLATE=utf8_czech_ci |

2. rely

注意: 数据库驱动版本要找自己对应的数据库驱动、我的是5.6

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!--    修改成我们所需要的mysql版本     -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
        <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>
        <!--   lombok     -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.0.5</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

3. Configure the SpringBoot database connection file

spring:
  datasource:
    # 我们这里用户名和密码都不需要双引号 ，
    username: root
    password: xxxx
    url: jdbc:mysql://localhost:3306/imagetest?userUnicode=true&characterEncoding=utf-8
    driver-class-name: com.mysql.jdbc.Driver

4. The configuration of the entity class is as follows

package com.jsxs.pojo;

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.io.Serializable;
import java.sql.Blob;

/**
 * @Author Jsxs
 * @Date 2023/4/2 20:54
 * @PackageName:com.jsxs.pojo
 * @ClassName: demo
 * @Description: TODO
 * @Version 1.0
 */
@Data
@AllArgsConstructor
@NoArgsConstructor
public class photo implements Serializable {
    
    
    @TableId(type = IdType.AUTO)
    private int id;
    private String images;
}

5. The Mapper layer needs to inherit a MybatisPlus interface

package com.jsxs.mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.jsxs.pojo.photo;
import org.apache.ibatis.annotations.Mapper;
import org.springframework.stereotype.Repository;

/**
 * @Author Jsxs
 * @Date 2023/4/3 14:45
 * @PackageName:com.jsxs.mapper
 * @ClassName: userMapper
 * @Description: TODO
 * @Version 1.0
 */
@Mapper
@Repository
public interface userMapper extends BaseMapper<photo> {
    
    
}

6. File Upload

    @Resource
    private userMapper mapper;  //mybatisplus 自带类
    
    // 文件上传
    @Test
    void testUpload() throws IOException {
    
    
        //  被上传的文件 - 真实开发中我们通过html获取被上传的路径
        String path="E:/加速器/2.jpg";
        // 读取被上传的文件
        FileInputStream fileInputStream = new FileInputStream(path);
        String  path2="E:/Ideal源码/Test-image/src/main/java/com/jsxs/upload"; // 读入到的文件位置
        String replace = UUID.randomUUID().toString().replace("-", ""); // UUID防止名字重复
        String realPath=path2 + "/" + replace + ".jpg"; // 真实被放去的位置
        FileOutputStream fileOutputStream = new FileOutputStream(realPath);
        // 数据库进行插入的操作
        photo p = new photo();
        p.setImages(realPath);
        mapper.insert(p);
        byte[] bytes = new byte[1024];  //缓冲区
        int count=0;
        while ((count=fileInputStream.read(bytes))!=-1){
    
    
            fileOutputStream.write(bytes,0,count);  // 上传到我们的 upload路径
        }
        fileInputStream.close();  // 关闭文件
        fileOutputStream.close();
    }

7. Download Document

    @Resource
    private userMapper mapper;  //mybatisplus 自带类

    //文件下载
    @Test
    void contextLoads() throws Exception {
    
    

        photo p = mapper.selectById(2);  // 查找数据库-通过ID
        //  读去文件
        FileInputStream fileInputStream = new FileInputStream(p.getImages()); //  读取我们查到的路径
        FileOutputStream fileOutputStream = new FileOutputStream("E:/加速器/4.jpg");  // 设置我们下载的路径
        byte[] bytes = new byte[20];  // 设置缓存区
        int count=0;
        while ((count=fileInputStream.read(bytes))!=-1){
    
    
            fileOutputStream.write(bytes,0,count);  // 文件下载到哪里?
        }
        fileInputStream.close();  // 关闭资源
        fileOutputStream.close();
    }