我正在尝试使用 Spring Reactive WebClient 将文件上传到 Spring 控制器。控制器非常简单,看起来像这样:
@PostMapping(value = "/upload", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
public ResponseEntity<String> uploadFile(
@RequestParam("multipartFile") MultipartFile multipartFile,
@RequestParam Map<String, Object> entityRequest
) {
entityRequest.entrySet().forEach(System.out::println);
System.out.println(multipartFile);
return ResponseEntity.ok("OK");
}
当我将此控制器与 cURL 一起使用时,一切正常
curl -X POST http://localhost:8080/upload -H 'content-type: multipart/form-data;' -F fileName=test.txt -F randomKey=randomValue -F multipartFile=@document.pdf
多部分文件转到正确的参数,其他参数转到映射。
当我尝试从WebClient执行相同的操作时,我卡住了。我的代码如下所示:
WebClient client = WebClient.builder().baseUrl("http://localhost:8080").build();
MultiValueMap<String, Object> map = new LinkedMultiValueMap<>();
map.set("multipartFile", new ByteArrayResource(Files.readAllBytes(Paths.get("/path/to/my/document.pdf"))));
map.set("fileName", "test.txt");
map.set("randomKey", "randomValue");
String result = client.post()
.uri("/upload")
.contentType(MediaType.MULTIPART_FORM_DATA)
.syncBody(map)
.exchange()
.flatMap(response -> response.bodyToMono(String.class))
.flux()
.blockFirst();
System.out.println("RESULT: " + result);
这会导致 400 错误
{
"timestamp":1510228507230,
"status":400,
"error":"Bad Request",
"message":"Required request part 'multipartFile' is not present",
"path":"/upload"
}
有谁知道如何解决这个问题?
自己找到了解决方案。事实证明,Spring 确实需要 Content-Disposition 标头来包含要序列化为控制器中的 MultipartFile 的上传的文件名。
为此,我必须创建一个支持设置文件名的 ByteArrayResource 子类
public class MultiPartResource extends ByteArrayResource {
private String filename;
public MultiPartResource(byte[] byteArray) {
super(byteArray);
}
public MultiPartResource(byte[] byteArray, String filename) {
super(byteArray);
this.filename = filename;
}
@Nullable
@Override
public String getFilename() {
return filename;
}
public void setFilename(String filename) {
this.filename = filename;
}
}
然后可以使用此代码在客户端中使用
WebClient client = WebClient.builder().baseUrl("http://localhost:8080").build();
MultiValueMap<String, Object> map = new LinkedMultiValueMap<>();
map.set("fileName", "test.txt");
map.set("randomKey", "randomValue");
ByteArrayResource resource = new MultiPartResource(Files.readAllBytes(Paths.get("/path/to/my/document.pdf")), "document.pdf");
String result = client.post()
.uri("/upload")
.contentType(MediaType.MULTIPART_FORM_DATA)
.body(BodyInserters.fromMultipartData(map))
.exchange()
.flatMap(response -> response.bodyToMono(String.class))
.flux()
.blockFirst();
System.out.println("RESULT: " + result);
提供内容处置的更简单方法
MultipartBodyBuilder builder = new MultipartBodyBuilder();
String header = String.format("form-data; name=%s; filename=%s", "paramName", "fileName.pdf");
builder.part("paramName", new ByteArrayResource(<file in byte array>)).header("Content-Disposition", header);
// in the request use
webClient.post().body(BodyInserters.fromMultipartData(builder.build()))
包含文件名到文件部分才能上传成功,并结合asyncPart()
以避免缓冲所有文件内容,然后您可以像这样编写代码:
WebClient client = WebClient.builder().baseUrl("http://localhost:8080").build();
Mono<String> result = client.post()
.uri("/upload")
.contentType(MediaType.MULTIPART_FORM_DATA)
.body((outputMessage, context) ->
Mono.defer(() -> {
MultipartBodyBuilder bodyBuilder = new MultipartBodyBuilder();
Flux<DataBuffer> data = DataBufferUtils.read(
Paths.get("/tmp/file.csv"), outputMessage.bufferFactory(), 4096);
bodyBuilder.asyncPart("file", data, DataBuffer.class)
.filename("filename.csv");
return BodyInserters.fromMultipartData(bodyBuilder.build())
.insert(outputMessage, context);
}))
.exchange()
.flatMap(response -> response.bodyToMono(String.class));
System.out.println("RESULT: " + result.block());
在这种情况下使用ByteArrayResource
效率不高,因为整个文件内容将加载到内存中。
使用带有 "file:"
前缀或ClassPathResource
的UrlResource
应该可以解决这两个问题。
UrlResource resource = new UrlResource("file:///path/to/my/document.pdf");