@GET("/greeting")
void getInternationalizedGreeting(@Header("Accept-Language") String languagePreference, Callback<Greeting> callback)
Define languagePreference
in a way your web server will understand, i.e. something like
da, en-gb;q=0.8, en;q=0.7`
See also here: http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.4.