How to set the produces value dynamically in spring rest controller? - spring

Question

I need to implement API which can either send response or download a file:
#GetMapping(value = "/download")
public ResponseEntity<?> downloadFile(
#RequestParam(value = "apiResponseType", required = true) String apiResponseType) throws IOException {
ValidationResponse response = null;
if (apiResponseType.equals("FILE")) {
String FILE_HEADER = "id,firstName,lastName,gender,age";
byte[] json = FILE_HEADER.getBytes();
Resource resource = new ByteArrayResource(json);
HttpHeaders headers = new HttpHeaders();
headers.setContentLength(resource.contentLength());
headers.setContentDispositionFormData("attachment", "test.csv");
return ResponseEntity.ok().headers(headers).contentType(MediaType.APPLICATION_OCTET_STREAM).body(resource);
} else {
response = new ValidationResponse();
response.setSuccess(true);
response.setMessage("TESTING");
return ResponseEntity.ok(response);
}
}
Above code is working for "ELSE" case. i.e., can able to send response.
But if I add "produces" to #GetMapping like below, I am able to download the file but not working for response (else case in above code) (Got status: 406 Not Acceptable):
#GetMapping(value = "/downloadFile", produces = MediaType.APPLICATION_OCTET_STREAM_VALUE)
Can anyone help me with this ?

Answer 1

Did you try return ResponseEntity.ok(response).contentType(MediaType.TEXT_PLAIN); on the else branch (and remove the produces)?

Answer 2

Your question has invalid assumption 'which can either send response or download a file'. Download file is nothing else that sending response! For API client it is no difference. For browser it is just implementation details if browser proposes to save the response as file or shows response in browser window.

Answer 3

Setting the MediaType via a call to contentType on the ResponeEntitiy no longer works. By now (SpringBoot 2.7.1) you have to set the MediaType to the headers.
I wrote this method to dynamically create headers with a given MediaType provided as a string.
final HttpHeaders httpHeaders = new HttpHeaders();
final MediaType mediaType;
switch (responseType) {
case "json":
mediaType = MediaType.APPLICATION_JSON;
break;
case "plain":
case "text":
mediaType = MediaType.TEXT_PLAIN;
break;
default:
final var parts = responseType.split("/");
if (parts.length < 2)
throw new IllegalArgumentException(String.format("Unrecognizable MediaType '%s'", responseType));
mediaType = new MediaType(parts[0], parts[1]);
break;
}
LOGGER.debug("Using mediaType {}", mediaType);
httpHeaders.setContentType(mediaType);