ResponseEntity does not accept return type "byte[]" but "ResponseEntity"

Question

I am trying to send data from one server to another one via REST endpoint:

Server B starts this request:

String resource = "http://...";
ResponseEntity<byte[]> response = restTemplate.getForObject(resource, byte[].class, customerID);

Server A receives the request and returns the file:

    ResponseEntity<byte[]> resp = new ResponseEntity<byte[]>(myByteArrayOutputStream.toByteArray(), HttpStatus.OK);
    return resp;

But I get an error at the.getForObject line:

Required Type: ResponseEntity[]
Provided: byte[]

So obviously I would have to change the statement to:

byte[] response = restTemplate.getForObject(resource, byte[].class, customerID);

or to

ResponseEntity<byte[]> response = restTemplate.getForObject(resource, ResponseEntity.class, customerID);

Then the error is gone but I lose the HttpStatus.Ok message at the response? What would be the proper solution here?

Answer 1

Yes, the getForObject method does not provide access to response metadata like headers and the status code. If you have to access this data, then use RestTemplate#getForEntity(url, responseType, uriVariables)

The RestTemplate#getForEntity returns a wrapper ResponseEntity<T> so you can read the response metadata and also read the body through the getBody() method.

ResponseEntity<byte[]> response = restTemplate.getForEntity(resource, byte[].class, customerID);
if (response.getStatusCode() == HttpStatus.OK) {
    byte[] responseContent = response.getBody();
    // ...
} else {
    // this is not very useful because for error codes (4xx and 5xx) the RestTemplate throws an Exception
}