Setting Authorization header in Spring RestTemplate

Question

I'm trying to to access a RestAPI-Endpoint with the help of Spring's RestTemplate

public List<Transaction> getTransactions() {
    // only a 24h token for the sandbox, so not security critical
    // still I replaced the last 10 digits here with 'x' but not in my original code
    String authToken = "tylhtvGM6Duy8q0ZBbGaTg2FZefLfyeEeMZvCXlU2bEiinnZcLSACTxxxxxxxxxx";
    String encodedAuthToken = Base64.getEncoder().encodeToString(authToken.getBytes());

    HttpHeaders headers = new HttpHeaders();
    headers.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));
    headers.add("Authorization", "Bearer "+encodedAuthToken );

    ResponseEntity<TransactionsResponse> response = restTemplate.exchange(
            "https://api-sandbox.starlingbank.com/api/v1/transactions",
            HttpMethod.GET,
            new HttpEntity<>("parameters", headers),
            TransactionsResponse.class
    );

    return response.getBody().getEmbedded().getTransactions();
}

but I get a HttpClientErrorException saying "403 Forbidden". Long version

Caused by: org.springframework.web.client.HttpClientErrorException: 403 Forbidden
    at org.springframework.web.client.DefaultResponseErrorHandler.handleError(DefaultResponseErrorHandler.java:94) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
    at org.springframework.web.client.DefaultResponseErrorHandler.handleError(DefaultResponseErrorHandler.java:79) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
    at org.springframework.web.client.ResponseErrorHandler.handleError(ResponseErrorHandler.java:63) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
    at org.springframework.web.client.RestTemplate.handleResponse(RestTemplate.java:766) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]

My code is based on a former stackoverflow thread and a call with the same parameters via Postman is successful:

So what is the problem?

Update

not encoding the authToken makes no difference

headers.add("Authorization", "Bearer tylhtvGM6Duy8q0ZBbGaTg2FZefLfyeEeMZvCXlU2bEiinnZcLSACTxxxxxxxxxx");

still leads to the same HttpClientErrorException: 403 Forbidden

Update2

I answered my question! (short version: UserAgent required. final code in anwser)

Answer 1

this particular server requires an UserAgent! The value can be whatever, but it has to be present!

So the final version is:

public List<Transaction> getTransactions() {
    // only a 24h token for the sandbox, so not security critical
    // still I replaced the last 10 digits here with 'x' but not in my original code
    String authToken = "tylhtvGM6Duy8q0ZBbGaTg2FZefLfyeEeMZvCXlU2bEiinnZcLSACTxxxxxxxxxx";

    HttpHeaders headers = new HttpHeaders();
    headers.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));        
    headers.add("User-Agent", "Spring's RestTemplate" );  // value can be whatever
    headers.add("Authorization", "Bearer "+authToken );

    ResponseEntity<TransactionsResponse> response = restTemplate.exchange(
            "https://api-sandbox.starlingbank.com/api/v1/transactions",
            HttpMethod.GET,
            new HttpEntity<>("parameters", headers),
            TransactionsResponse.class
    );

    return response.getBody().getEmbedded().getTransactions();
}

Answer 2

You are encoding your token in Base64 and its already encoded, your code is based in this but in this example they are encoding a Basic Authorization header with (user:password) encoded

probe this

 HttpHeaders headers = new HttpHeaders();
    headers.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));
    headers.add("Authorization", "Bearer "+ authToken );

Answer 3

If you are using OAuth Bearer tokens for authentication you don't need to encode them prior to making the request. The following line should be sufficient:

headers.add("Authorization", "Bearer " + authToken);

The code you mentioned has Http Basic authentication which consists of sending the credentials as username:password pair encoded with Base64.