Spring Boot实现文件上传和下载

1.背景

项目中经常会有上传和下载的需求，这篇文章简述一下springboot项目中实现简单的上传和下载。

2.代码工程

实验目标

实现简单的文件上传和下载

pom.xml

<?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">
    <parent>
        <artifactId>springboot-demo</artifactId>
        <groupId>com.et</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>
 
    <artifactId>file</artifactId>
 
    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
 
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-autoconfigure</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpclient</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpmime</artifactId>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
    </dependencies>
</project>

controller

Web项目中，文件的上传和下载服务也是基于HTTP请求的，文件上传由于需要向服务接口提交数据，可以使用POST的请求方式，而文件的下载只是获取数据，因此可以使用GET请求方式。  

package com.et.controller;
 
import com.et.bean.FileInfo;
import com.et.service.FileUploadService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.io.Resource;
import org.springframework.http.HttpHeaders;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.multipart.MultipartFile;
 
import java.util.HashMap;
import java.util.List;
import java.util.Map;
 
@RestController
public class HelloWorldController {
    @RequestMapping("/hello")
    public Map<String, Object> showHelloWorld(){
        Map<String, Object> map = new HashMap<>();
        map.put("msg", "HelloWorld");
        return map;
    }
    @Autowired
    private FileUploadService fileUploadService;
 
 
    /**
     * upload
     *
     * @param files
     * @return
     */
    @PostMapping("/upload")
    public ResponseEntity<String> upload(@RequestParam("files") MultipartFile[] files) {
        fileUploadService.upload(files);
        return ResponseEntity.ok("File Upload Success");
    }
 
    /**
     *  files
     *
     * @return
     */
    @GetMapping("/files")
    public ResponseEntity<List<FileInfo>> list() {
        return ResponseEntity.ok(fileUploadService.list());
    }
 
    /**
     * get file by name
     *
     * @param fileName
     * @return
     */
    @GetMapping("/files/{fileName:.+}")
    public ResponseEntity<Resource> getFile(@PathVariable("fileName") String fileName) {
        return ResponseEntity.ok().header(HttpHeaders.CONTENT_DISPOSITION,
                "attachment; filename=\"" + fileName + "\"").body(fileUploadService.getFile(fileName));
    }
}

service

创建好指定的文件存放路径文件夹后，上传逻辑只需要将接收到的文件数据赋值到指定路径后即可。

file.getInputStream()，接收文件参数的对应字节流

this.path.resolve(file.getOriginalFilename())，指定的path路径拼接接收文件的原始名称作为文件的路径信息

Files.copy()，复制文件的方法

文件的下载逻辑是根据指定的文件名称到文件资源文件夹中获取，如果存在则返回文件。

this.path.resolve(fileName)，构建文件全路径

new UrlResource(file.toUri())，根据文件路径创建URL源

resource.exists() && resource.isReadable()，文件存在并且可读时返回

package com.et.service;
 
import com.et.bean.FileInfo;
import org.springframework.core.io.Resource;
import org.springframework.web.multipart.MultipartFile;
 
import java.util.List;
 
 
public interface FileUploadService {
 
    void upload(MultipartFile[] files);
 
    List<FileInfo> list();
 
    Resource getFile(String fileName);
}
package com.et.service.impl;
 
import com.et.bean.FileInfo;
import com.et.service.FileUploadService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.core.io.FileSystemResource;
import org.springframework.core.io.Resource;
import org.springframework.stereotype.Service;
import org.springframework.util.FileCopyUtils;
import org.springframework.web.multipart.MultipartFile;
 
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
 
@Service
@Slf4j
public class FileUploadServiceImpl implements FileUploadService {
    @Value("${upload.path:/data/upload/}")
    private String filePath;
 
    private static final List<FileInfo> FILE_STORAGE = new CopyOnWriteArrayList<>();
 
    @Override
    public void upload(MultipartFile[] files) {
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        for (MultipartFile file : files) {
            String fileName = file.getOriginalFilename();
            boolean match = FILE_STORAGE.stream().anyMatch(fileInfo -> fileInfo.getFileName().equals(fileName));
            if (match) {
                throw new RuntimeException("File [ " + fileName + " ] already exist");
            }
 
            String currentTime = simpleDateFormat.format(new Date());
            try (InputStream in = file.getInputStream();
                 OutputStream out = Files.newOutputStream(Paths.get(filePath + fileName))) {
                FileCopyUtils.copy(in, out);
            } catch (IOException e) {
                log.error("File [{}] upload failed", fileName, e);
                throw new RuntimeException(e);
            }
            FileInfo fileInfo = new FileInfo().setFileName(fileName).setUploadTime(currentTime);
            FILE_STORAGE.add(fileInfo);
        }
    }
 
    @Override
    public List<FileInfo> list() {
        return FILE_STORAGE;
    }
 
    @Override
    public Resource getFile(String fileName) {
        FILE_STORAGE.stream()
                .filter(info -> info.getFileName().equals(fileName))
                .findFirst()
                .orElseThrow(() -> new RuntimeException("File [ " + fileName + " ] not exist"));
        File file = new File(filePath + fileName);
        return new FileSystemResource(file);
    }
}
application.properties
spring.servlet.multipart.max-file-size=150MB
spring.servlet.multipart.max-request-size=200MB
spring.servlet.multipart.file-size-threshold=100MB
upload.path=/Users/liuhaihua/tmp/

以上只是一些关键代码，所有代码请参见下面代码仓库

代码仓库

https://github.com/Harries/springboot-demo（File）

3.测试

启动Spring Boot应用

使用postman请求下载接口时，接口返回文件，postman会直接解析文件内容，如果无法正确解析则会显示乱码信息。如果在浏览器请求接口时，返回文件时浏览器会弹出下载文件的提示。

上传测试

下载测试

4.引用

https://github.com/callicoder/spring-boot-file-upload-download-rest-api-example

Spring Boot实现文件上传和下载 | Harries Blog™