Retrofit: POST request not receiving response body

[kal4l]

I have an API for users, and whenever you create a user, it returns the user created. I can see this behavior using a Client such as Postman:

POST {endpoint}/users
Body:

{"email":"[email protected]","experience":0, ...}

---

Response Body:

{
  "name": "Kevin Grant",
  "email": "[email protected]",
  ...
}

Content-Length → 1014
Content-Type → application/hal+json;charset=UTF-8
Date → Sat, 02 Apr 2016 22:23:41 GMT
Location → {endpoint}/users/5700466d288714814cccc661
...

However, when POSTing with Retrofit, the post is made correctly and 201 Created is received, but the Content-Length is always 0:

@POST("users")
Observable<User> createUser(@Body User user);

Api.getService().createUser(user)
            .subscribeOn(Schedulers.newThread())
            .observeOn(AndroidSchedulers.mainThread())
            .doOnError(e -> Log.i(TAG, "ERROR: " + e.getMessage()))
            .subscribe(this::logUser);

The previous code results in the logs:

04-05 19:40:31.004  D/OkHttp: --> POST {endpoint}/users HTTP/1.1
04-05 19:40:31.004  D/OkHttp: Content-Type: application/json; charset=UTF-8
04-05 19:40:31.004  D/OkHttp: Content-Length: 337
04-05 19:40:31.014  D/OkHttp: {"averages":null,"email":"[email protected]","experience":0,"friends":null,"googleId":"12345","id":null,"imageUrl":"url.com","incomingRequests":null,"level":0,"matchLosses":0,"matchWins":0,"matches":null,"name":"Kevin","outgoingRequests":null,"records":null,"registrationToken":"1233213","series":null,"seriesLosses":0,"seriesWins":0}
04-05 19:40:31.014  D/OkHttp: --> END POST (337-byte body)

04-05 19:40:31.544  D/OkHttp: <-- 201 Created {endpoint}/users (530ms)
04-05 19:40:31.544  D/OkHttp: Content-Length: 0
04-05 19:40:31.544  D/OkHttp: Location: {endpoint}/users/5704771f2887369e3b9325a3
04-05 19:40:31.544  D/OkHttp: Server: Microsoft-IIS/8.0
04-05 19:40:31.544  D/OkHttp: X-Powered-By: ASP.NET
04-05 19:40:31.544  D/OkHttp: Set-Cookie: ARRAffinity=a03ce629965ea3ff1ee2a6b1d2c9ce9e2200484a00fde7db350decd224781f9f;Path=/;Domain={endpoint}
04-05 19:40:31.544  D/OkHttp: Date: Wed, 06 Apr 2016 02:40:31 GMT
04-05 19:40:31.544  D/OkHttp: OkHttp-Sent-Millis: 1459910431421
04-05 19:40:31.544  D/OkHttp: OkHttp-Received-Millis: 1459910431547
04-05 19:40:31.544  D/OkHttp: <-- END HTTP (0-byte body)
04-05 19:40:31.554 26552-26552/ I/SECOND ACTIVITY: ERROR: No content to map due to end-of-input
                                                                                    at [Source: java.io.InputStreamReader@c3a1fa2; line: 1, column: 0]

Which shows the request was successfully made, but shows an empty response body. This of course throws an error, trying to parse the response into a User object.

This seems like an issue to me, as as far as I can tell, and after research, my code is effectively correct.

[JakeWharton]

I would guess Postman is making a follow-up request using the 201's Location header value and hiding that redirect from you.

[JakeWharton]

Not sure whether it's reasonable to always do this. That would prevent you from accessing the optional entity from the 201 itself.

I need to do more research.

For now change your type to Observable<Response<Void>> and use the Location header of the Response to flatMap a follow-up request using an endpoint like:

@GET
Observable<User> lookupUser(@Url String url);

[kal4l]

Jake, the quick response is greatly appreciated. Your solution worked perfectly! Thank you so much.

[matbos]

You can also leverage the OkHttp's ability to follow redirects for 3xx codes using the interceptor below added as a network interceptor to OkHttpClient.

package pl.matbos.exemplary.util;

import java.io.IOException;

import okhttp3.Interceptor;
import okhttp3.Request;
import okhttp3.Response;
import retrofit2.http.Header;

import static java.net.HttpURLConnection.HTTP_CREATED;
import static java.net.HttpURLConnection.HTTP_SEE_OTHER;

/**
 * To utilize it simply add a header to your endpoint using {@link Header} annotation:
 * <pre><code>
 * interface MyService {
 *   &#64;POST("user")
 *   &#64;Headers(Follow201LocationInterceptor.FOLLOW_HEADER)
 *   Observable&lt;User&gt; createUser(@Body String name)
 * }
 * </code></pre>
 * <p>
 * It has to be used as a network interceptor, otherwise it will not work.
 */
public class Follow201LocationInterceptor implements Interceptor {

    private static final String FOLLOW_REDIRECT = "follow-redirect";
    public static final String FOLLOW_HEADER = FOLLOW_REDIRECT + ":true";
    private static final String LOCATION = "Location";

    @Override
    public Response intercept(Chain chain) throws IOException {
        Request request = chain.request();
        boolean shouldRedirect = request.header(FOLLOW_REDIRECT) != null;

        if (shouldRedirect) {
            request = request.newBuilder().removeHeader(FOLLOW_REDIRECT).build();
        }

        Response response = chain.proceed(request);
        if (shouldRedirect && response.code() == HTTP_CREATED && response.header(LOCATION) != null) {
            return response.newBuilder().code(HTTP_SEE_OTHER).build();
        }
        return response;
    }
}

And adding(to methods that should redirect) the following header @Headers(Follow201LocationInterceptor.FOLLOW_HEADER).
So the endpoint definition would look like this:

    @POST("user")
    @Headers(Follow201LocationInterceptor.FOLLOW_HEADER)
    Observable<User> registerUser();

[JakeWharton]

The interceptor (and optional marker header) is a great way to opt in to this behavior. Retrofit can't do anything automatic here because the 201 might return some body that the application-layer cares about.

[paramrana78]

Hello there,

Even I'm not able to get a response using retrofit, while it gives a success response as:

Response{protocol=http/1.1, code=201, message=Created, url=http://test.some_url.in/api/upload/user/PostUserImage/}

and the image is successfully uploaded to server but
Nothing is shown either in response body or using Gson:

I'm using following code:

`
private void uploadImage(byte[] imageBytes) {

    Retrofit retrofit = new Retrofit.Builder()
            .baseUrl(URL)
            .addConverterFactory(GsonConverterFactory.create())
            .build();

    RetrofitInterface retrofitInterface = retrofit.create(RetrofitInterface.class);

    RequestBody requestFile = RequestBody.create(MediaType.parse("image/jpeg"), imageBytes);

    MultipartBody.Part body = MultipartBody.Part.createFormData("image", "unnamed.jpg", requestFile);
    Call<Response> call = retrofitInterface.uploadImage(body);
    mProgressBar.setVisibility(View.VISIBLE);
    call.enqueue(new Callback<Response>() {
        @Override
        public void onResponse(Call<Response> call, retrofit2.Response<Response> response) {

            mProgressBar.setVisibility(View.GONE);

            Log.v("keys","-----response---------"+response);
            if (response.isSuccessful()) {

                Response responseBody = response.body();
                mBtImageShow.setVisibility(View.VISIBLE);
                assert responseBody != null;

            } else {

                ResponseBody errorBody = response.errorBody();

                Gson gson = new Gson();

                assert errorBody != null;
                Response errorResponse = gson.fromJson(errorBody.toString(), Response.class);


            }
        }

        @Override
        public void onFailure(Call<Response> call, Throwable t) {

            mProgressBar.setVisibility(View.GONE);
            Log.d(TAG, "onFailure: "+t.getLocalizedMessage());
        }
    });
} `

Please help how can I get the server response??????