Caused by: retrofit.RetrofitError: method POST must have a request body

Question

I am using retrofit to make a post api call, I am getting the following error while trying to hit the endpoint.

     Caused by: rx.exceptions.OnErrorNotImplementedException: method POST must have a request body.
            at rx.Observable$30.onError(Observable.java:7334)
            at rx.observers.SafeSubscriber._onError(SafeSubscriber.java:154)
            at rx.observers.SafeSubscriber.onError(SafeSubscriber.java:111)
            at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber.pollQueue(OperatorObserveOn.java:197)
            at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber$2.call(OperatorObserveOn.java:173)
            at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:55)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at 
     Caused by: java.lang.IllegalArgumentException: method POST must have a request body.
            at com.squareup.okhttp.Request$Builder.method(Request.java:236)
            at retrofit.client.OkClient.createRequest(OkClient.java:59)
            at retrofit.client.OkClient.execute(OkClient.java:53)
            at retrofit.RestAdapter$RestHandler.invokeRequest(RestAdapter.java:326)

trying to access a post api

 @POST("/service/v2/auth/ip-address")
    rx.Observable<AuthState> verifyIP();

actual api call

LoginService service = CKRestClient.get().create(LoginService.class);
            service.verifyIP().observeOn(AndroidSchedulers.mainThread()).subscribe(
                    new Action1<AuthState>() {
                        @Override
                        public void call(AuthState authState) {

                        }
                    });
        });

Answer 1

It looks like Retrofit wants POST requests to have a payload. There's already an issue for it: https://github.com/square/retrofit/issues/854

As a workaround, you could do something like this:

@POST("/service/v2/auth/ip-address")
rx.Observable<AuthState> verifyIP(@Body Object dummy);

and then do:

LoginService service = CKRestClient.get().create(LoginService.class);

service.verifyIP(null).observeOn(AndroidSchedulers.mainThread()).subscribe(
  new Action1<AuthState>() {
    @Override
    public void call(AuthState authState) {
      // ...
    }
  });
});

Or, if service.verifyIP(null) throws a NPE, replace it with service.verifyIP("") or similar.