Spring Boot 实现本地文件上传

本文介绍如何在 Spring Boot 应用中实现本地文件上传功能。包括配置文件设置、配置类、控制器、响应类和服务类的实现。

1. 设置上传文件配置

在 application.yml 中配置文件上传的相关参数：

yaml

spring:
  servlet:
    multipart:
      max-file-size: 5MB
      max-request-size: 10MB

# 上传目录
file:
  upload-dir: /Users/jasonz/Downloads/qxt

2. 配置类

FileStorageProperties

定义一个配置类来读取上传目录的配置：

java

import org.springframework.boot.context.properties.ConfigurationProperties;

@ConfigurationProperties(prefix = "file")
public class FileStorageProperties {
    private String uploadDir;

    public String getUploadDir() {
        return uploadDir;
    }

    public void setUploadDir(String uploadDir) {
        this.uploadDir = uploadDir;
    }
}

3. 开启配置读取

在应用程序主类中启用配置读取：

java

import com.example.filedemo.property.FileStorageProperties;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.properties.EnableConfigurationProperties;

@SpringBootApplication
@EnableConfigurationProperties({
    FileStorageProperties.class
})
public class FileDemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(FileDemoApplication.class, args);
    }
}

4. 控制器

FileController

创建一个控制器来处理文件上传和下载请求：

java

import com.example.filedemo.payload.UploadFileResponse;
import com.example.filedemo.service.FileStorageService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.io.Resource;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.servlet.support.ServletUriComponentsBuilder;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

@RestController
public class FileController {
    private static final Logger logger = LoggerFactory.getLogger(FileController.class);

    @Autowired
    private FileStorageService fileStorageService;

    @PostMapping("/uploadFile")
    public UploadFileResponse uploadFile(@RequestParam("file") MultipartFile file) {
        String fileName = fileStorageService.storeFile(file);
        String fileDownloadUri = ServletUriComponentsBuilder.fromCurrentContextPath()
                .path("/downloadFile/")
                .path(fileName)
                .toUriString();
        return new UploadFileResponse(fileName, fileDownloadUri, file.getContentType(), file.getSize());
    }

    @PostMapping("/uploadMultipleFiles")
    public List<UploadFileResponse> uploadMultipleFiles(@RequestParam("files") MultipartFile[] files) {
        return Arrays.asList(files)
                .stream()
                .map(file -> uploadFile(file))
                .collect(Collectors.toList());
    }

    @GetMapping("/downloadFile/{fileName:.+}")
    public ResponseEntity<Resource> downloadFile(@PathVariable String fileName, HttpServletRequest request) {
        // Load file as Resource
        Resource resource = fileStorageService.loadFileAsResource(fileName);

        // Try to determine file's content type
        String contentType = null;
        try {
            contentType = request.getServletContext().getMimeType(resource.getFile().getAbsolutePath());
        } catch (IOException ex) {
            logger.info("Could not determine file type.");
        }

        // Fallback to the default content type if type could not be determined
        if (contentType == null) {
            contentType = "application/octet-stream";
        }

        return ResponseEntity.ok()
                .contentType(MediaType.parseMediaType(contentType))
                .header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"" + resource.getFilename() + "\"")
                .body(resource);
    }
}

5. 响应类

UploadFileResponse

定义一个响应类用于返回上传文件的信息：

java

public class UploadFileResponse {
    private String fileName;
    private String fileDownloadUri;
    private String fileType;
    private long size;

    public UploadFileResponse(String fileName, String fileDownloadUri, String fileType, long size) {
        this.fileName = fileName;
        this.fileDownloadUri = fileDownloadUri;
        this.fileType = fileType;
        this.size = size;
    }

    // Getters and Setters (Omitted for brevity)
}

6. 服务类

FileStorageService

实现文件存储和加载的服务类：

java

import com.example.filedemo.exception.FileStorageException;
import com.example.filedemo.exception.MyFileNotFoundException;
import com.example.filedemo.property.FileStorageProperties;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.io.Resource;
import org.springframework.core.io.UrlResource;
import org.springframework.stereotype.Service;
import org.springframework.util.StringUtils;
import org.springframework.web.multipart.MultipartFile;
import java.io.IOException;
import java.net.MalformedURLException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardCopyOption;

@Service
public class FileStorageService {
    private final Path fileStorageLocation;

    @Autowired
    public FileStorageService(FileStorageProperties fileStorageProperties) {
        this.fileStorageLocation = Paths.get(fileStorageProperties.getUploadDir())
                .toAbsolutePath().normalize();

        try {
            Files.createDirectories(this.fileStorageLocation);
        } catch (Exception ex) {
            throw new FileStorageException("Could not create the directory where the uploaded files will be stored.", ex);
        }
    }

    public String storeFile(MultipartFile file) {
        // Normalize file name
        String fileName = StringUtils.cleanPath(file.getOriginalFilename());

        try {
            // Check if the file's name contains invalid characters
            if (fileName.contains("..")) {
                throw new FileStorageException("Sorry! Filename contains invalid path sequence " + fileName);
            }

            // Copy file to the target location (Replacing existing file with the same name)
            Path targetLocation = this.fileStorageLocation.resolve(fileName);
            Files.copy(file.getInputStream(), targetLocation, StandardCopyOption.REPLACE_EXISTING);
            return fileName;
        } catch (IOException ex) {
            throw new FileStorageException("Could not store file " + fileName + ". Please try again!", ex);
        }
    }

    public Resource loadFileAsResource(String fileName) {
        try {
            Path filePath = this.fileStorageLocation.resolve(fileName).normalize();
            Resource resource = new UrlResource(filePath.toUri());

            if (resource.exists()) {
                return resource;
            } else {
                throw new MyFileNotFoundException("File not found " + fileName);
            }
        } catch (MalformedURLException ex) {
            throw new MyFileNotFoundException("File not found " + fileName, ex);
        }
    }
}

7. 异常类

FileStorageException

自定义异常类用于处理文件存储错误：

java

public class FileStorageException extends RuntimeException {
    public FileStorageException(String message) {
        super(message);
    }

    public FileStorageException(String message, Throwable cause) {
        super(message, cause);
    }
}

MyFileNotFoundException

自定义异常类用于处理文件未找到错误：

java

import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.ResponseStatus;

@ResponseStatus(HttpStatus.NOT_FOUND)
public class MyFileNotFoundException extends RuntimeException {
    public MyFileNotFoundException(String message) {
        super(message);
    }

    public MyFileNotFoundException(String message, Throwable cause) {
        super(message, cause);
    }
}