Retrofit (como eu uso)

Retrofit.java

            RequestInterceptor requestInterceptor = new RequestInterceptor() {
                @Override
                public void intercept(RequestFacade request) {
                    request.addHeader("Content-Type", "application/json");
                    //request.addHeader("Authorization", tokenApp);
                }
            };

            RestAdapter restAdapter = new RestAdapter.Builder()
                    .setEndpoint(Configs.getAddressApi())
                    .setRequestInterceptor(requestInterceptor)
                    .setLogLevel(RestAdapter.LogLevel.FULL)
                    .build();