MultipartFile 文件下载

您可以使用Spring框架提供的`MultipartFile`来处理文件下载。以下是一个简单的示例代码：

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.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.servlet.mvc.method.annotation.MvcUriComponentsBuilder;
import org.springframework.web.servlet.mvc.method.annotation.ResponseBodyEmitter;
import org.springframework.web.servlet.mvc.method.annotation.StreamingResponseBody;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;
import java.util.stream.Collectors;

@RestController
@RequestMapping("/files")
public class FileController {
    
    private static final String FILE_STORAGE_PATH = "/path/to/your/file/storage/directory";
    
    @GetMapping
    public List<String> getAllFiles() throws IOException {
        return Files.walk(Paths.get(FILE_STORAGE_PATH))
                .filter(Files::isRegularFile)
                .map(Path::toString)
                .collect(Collectors.toList());
    }
    
    @GetMapping("/{filename:.+}")
    public ResponseEntity<Resource> downloadFile(@PathVariable String filename) throws IOException {
        Path filePath = Paths.get(FILE_STORAGE_PATH).resolve(filename);
        Resource resource = new UrlResource(filePath.toUri());
        
        if (resource.exists()) {
            return ResponseEntity.ok()
                    .header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"" + resource.getFilename() + "\"")
                    .contentType(MediaType.APPLICATION_OCTET_STREAM)
                    .body(resource);
        } else {
            return ResponseEntity.notFound().build();        }
    }
}

上述示例代码中，`getAllFiles`方法返回文件存储目录下的所有文件列表。`downloadFile`方法用于下载指定的文件，它根据文件名构建文件路径，并将文件作