HttpClient, Unirest and a 403 in Kotlin

Question

I am trying to understand the following problem when issuing a GET-request to an API in Kotlin.

When sending the request with Unirest ...

val response: com.mashape.unirest.http.HttpResponse<String>? =
  Unirest.get(url)
    .header(
      headerKey,
      headerValue
    )
    .asString()

response?.let {
  println("${response.code}")
}

... I get a response code of 200. All fine.

But when I send it with HttpClient ...

val client = HttpClient.newBuilder().build();
val request = HttpRequest.newBuilder()
  .uri(URI.create(url))
  .GET()
  .header(
    headerKey,
    headerValue
  )
  .build()
val response = client.send(request, HttpResponse.BodyHandlers.ofString());
println(response.statusCode())

... the response code is 403! Same when I am using Retrofit and OkHttp.

The headerKey is "Authorization" and headerValue is "Bearer ...somekey...".

What am I missing?

Answer 1

Found the issue and it was simple: The user agent was missing in the header.

Therefore I had to add this line to the request-instantiation:

.header("User-Agent", "HttpClient")

Here is the full example:

val client = HttpClient.newBuilder().build()
val request = HttpRequest.newBuilder()
  .uri(URI.create(url))
  .GET()
  .header(authHeaderKey, authHeaderValue)
  .header("User-Agent", "HttpClient")
  .build()
val response = client.send(request, HttpResponse.BodyHandlers.ofString());
println(response.statusCode())