I am trying to upload a file in chunks in Java.
My chunk upload function:
@Async
private Future<String> sendChunk(byte[] chunk, int start, int end, int numberOfChunks, String name, String sessionId) throws IOException {
LinkedMultiValueMap<String, Object> requestParams = new LinkedMultiValueMap<>();
requestParams.add("data", new String(java.util.Base64.getEncoder().encode(chunk), "UTF-8"));
requestParams.add("start", start);
requestParams.add("end", end);
requestParams.add("numberOfChunks", numberOfChunks);
requestParams.add("fileName", name);
requestParams.add("session", sessionId);
HttpEntity<LinkedMultiValueMap<String, Object>> requestEntity = new HttpEntity<>(requestParams);
UploadResponse uploadResponse = restTemplate.exchange(fileServiceUrl, HttpMethod.POST, requestEntity, new ParameterizedTypeReference<UploadResponse>(){}).getBody();
return new AsyncResult<>(uploadResponse.getSessionId());
}
This is how the File-Service-API looks like:
@RequestMapping(value = "/simpleUploader", method = RequestMethod.POST, produces = "application/json")
public ResponseEntity<UploadResponse> simpleUploader(
@RequestParam("data") String data,
@RequestParam("session") String sessionId,
@RequestParam("start") int start,
@RequestParam("end") int end,
@RequestParam("numberOfChunks") int numberOfChunks,
@RequestParam("fileName") String fileName) throws IOException {
....
}
Now, if I try to upload a Chunk the File-Service responds with a 400 - Bad Request.
Stack-Trace:
org.springframework.web.client.HttpClientErrorException: 400 null at org.springframework.web.client.DefaultResponseErrorHandler.handleError(DefaultResponseErrorHandler.java:91) at org.springframework.web.client.RestTemplate.handleResponse(RestTemplate.java:667) at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:620) at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:580) at org.springframework.web.client.RestTemplate.exchange(RestTemplate.java:526)
It will be rejected from Spring even before it gets to the API-Function.
I am already uploading the same way, but in Javascript. From Javascript everything is working as it should.
What am I missing?
The only problem I had with my code was, that "sessionId" will be null the first time I am calling the File-Service API.
When I set a value of a Map Entry to null, the whole Entry doesn't get passed. I didnt knew that.
My fix was to add a defaultValue to @RequestParam("session") String sessionId so that the method declaration looks like that:
@RequestMapping(value = "/simpleUploader", method = RequestMethod.POST, produces = "application/json")
public ResponseEntity<UploadResponse> simpleUploader(
...
@RequestParam(value = "session", defaultValue = "") String sessionId,
... ) throws IOException {
....
}
The @Async has two limitations.
http://www.baeldung.com/spring-async
Try changing private to public
@Async
public Future<String> sendChunk(byte[] chunk, int start, int end, int numberOfChunks, String name, String sessionId) throws IOException {