[RFC] Easier creation of new calls

[christophehenry]

Creating new Call<T> is far too difficult. Currently, it requires creating a new class implementing Call. Vut this is not handy in the case you just want to modify the call at run-time according to custom annotations using adapters.

[JakeWharton]

Can you explain your use case more?

[christophehenry]

Sure! So I have an HTTP API that mainly work with short-lived tokens for authentication. This token must be retrieved by calling an endpoint secured by a basic authentication. I wanted to use custom annotation to:

• intercept the calls to the HTTP API and renew the token if necessary before performing the actual call
• dynamically set the authentication header when calling the token endpoint.

Now I know that the second use case can be handled by using a @Header parameter. But since I also have the first use case, my service implementation class has the credentials in its properties. I also know That both these use case can be handled by an interceptor, as described here, but not every endpoint requires the same authentication. So I would have to add a lot of logic to determine which endpoint is being called and which pre-processing it requires.

I ended up trying to distinguish the endpoints authenticated by a token from the token endpoint authenticated by a basic authentication using custom annotations and, unless I'm wrong, OkHttpClient's Interceptor won't have acces to annotations.

[swankjesse]

Does Invocation help?
https://square.github.io/retrofit/2.x/retrofit/retrofit2/Invocation.html

 class InvocationLogger implements Interceptor {
   @Override public Response intercept(Chain chain) throws IOException {
     Request request = chain.request();
     Invocation invocation = request.tag(Invocation.class);
     if (invocation != null) {
       System.out.printf("%s.%s %s%n",
           invocation.method().getDeclaringClass().getSimpleName(),
           invocation.method().getName(), invocation.arguments());
     }
     return chain.proceed(request);
   }
 }

[christophehenry]

@swankjesse Oh nice! That works well! Maybe this use-case could be worth documenting?
Thank you both a lot for taking time to answer to me 👍