spring webflux文件上传与下载

1、文件上传：

Controller：

 @PostMapping("/import")
    public void importImage(@RequestPart("file") FilePart filePart) {
        imageService.importImage(filePart);
    }

Service：

   public void importImage(FilePart filePart) {
        File saveFile = new File("/tmp/a.txt");
        if (!copyFile(filePart, saveFile)) {
            throw new OpsManagerException("文件保存失败!");
        }
    }

public boolean copyFile(FilePart filePart, File tempFile) {
        try {
            if (tempFile.exists()) {
                tempFile.delete();
            }
            tempFile.createNewFile();
            AsynchronousFileChannel channel = AsynchronousFileChannel.open(tempFile.toPath(), StandardOpenOption.WRITE);
            AtomicBoolean copyFinish = new AtomicBoolean(false);
            DataBufferUtils.write(filePart.content(), channel, 0).doOnComplete(() -> copyFinish.set(true)).subscribe();
            AtomicInteger atomicInteger = new AtomicInteger(0);
            while (!copyFinish.get()) {
                Thread.sleep(5000);
                atomicInteger.addAndGet(1);
                if (atomicInteger.get() > 720) {
                    throw new OpsManagerException("文件过大");
                }
            }
            return true;
        } catch (Exception e) {
            log.error("save upload file error", e);
            return false;
        }
    }

2、文件下载：

Controller：

  @GetMapping("/export")
    public Mono<Void> downloadFile(ServerHttpResponse response) {
        File file = new File("/tmp/workplace.zip");
        return TaskUtils.downloadFile(file, response);
    }

Service：

public static Mono<Void> downloadFile(File file, ServerHttpResponse response) {
        try {
            response.getHeaders().set(HttpHeaders.CONTENT_DISPOSITION, "attachment;filename=" + URLEncoder.encode(file.getName(), "UTF-8"));
            response.getHeaders().setContentType(MediaType.APPLICATION_OCTET_STREAM);
            response.getHeaders().set(HttpHeaders.CONTENT_LENGTH, "" + file.length());
            Flux<DataBuffer> dataBufferFlux = Flux.create((FluxSink<DataBuffer> emitter) -> {
                InputStream in = null;
                try {
                    int bytesRead;
                    in = new FileInputStream(file);
                    byte[] buffer = new byte[1024 * 1024];
                    while ((bytesRead = in.read(buffer)) != -1) {
                        emitter.next(response.bufferFactory().wrap(Arrays.copyOf(buffer, bytesRead)));
                    }
                    emitter.complete();
                } catch (IOException e) {
                    emitter.error(e);
                } finally {
                    if (in != null) {
                        try {
                            in.close();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }
                }
            });
            return response.writeAndFlushWith(Mono.just(dataBufferFlux));
        } catch (IOException ex) {
            logger.error("download file error!", ex);
            throw new RuntimeException("download file error!");
        }
    }

上面的文件下载，可能会由于垃圾回收不及时，而导致OOM，则可以使用以下代码；

import org.springframework.core.io.Resource;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.http.codec.multipart.FilePart;
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 reactor.core.publisher.Mono;

import java.nio.file.Path;
import java.nio.file.Paths;

@RestController
@RequestMapping("/files")
public class FileController {

    // 示例：将文件直接返回给客户端
    @GetMapping("/{filename}")
    public Mono<ResponseEntity<Resource>> downloadFile(@PathVariable String filename) {
        // 你可能需要将文件路径配置为适应你的环境
        String filePath = "/path/to/your/files/" + filename;
        Path path = Paths.get(filePath);
        Resource resource = new org.springframework.core.io.PathResource(path);

        return Mono.just(ResponseEntity.ok()
                .contentType(MediaType.APPLICATION_OCTET_STREAM)
                .body(resource));
    }

    // 示例：通过FormData方式上传文件，然后将文件直接返回给客户端
    @PostMapping("/upload")
    public Mono<ResponseEntity<Resource>> uploadFile(@RequestPart("file") FilePart filePart) {
        // 保存文件到服务器，这里简化为直接返回文件
        Resource resource = new InputStreamResource(filePart.content());

        return Mono.just(ResponseEntity.ok()
                .contentType(MediaType.APPLICATION_OCTET_STREAM)
                .body(resource));
    }
}

当然下载完后还可以回调，例如做一些删除文件之类的什么（此时resource不能放在body中，否则会回调失败）：

mono
    .doOnSuccess(value -> {
        // 在成功时执行回调
        System.out.println("Success: " + value);
    })
    .doOnError(error -> {
        // 在出错时执行回调
        System.err.println("Error: " + error.getMessage());
    })
    .subscribe();  // 订阅Mono

而正确代码为（这里就是多了个header）：

 public static Mono<ResponseEntity> downloadFile2(String filePath) {
        // 保存文件到服务器，这里简化为直接返回文件
        HttpHeaders headers = new HttpHeaders();
        Path path = Paths.get(filePath);
        headers.set(HttpHeaders.CONTENT_DISPOSITION, "attachment;filename=" + URLEncoder.encode(file.getName(), "UTF-8"));
        headers.set(HttpHeaders.CONTENT_LENGTH, "" + file.length());
        headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
        Resource resource = new PathResource(path);
        ResponseEntity entity = new ResponseEntity<>(resource, HttpStatus.OK);
        return Mono.just(entity).doFinally(signalType -> System.out.println("完成了！！！"));
    }