zeroc-ice
Simplify DispatchInterceptor API
Dispatch interceptors are currently a separate servant abstract class: the application-code derives from DispatchInterceptor, implements dispatch, and calls ice_dispatch on the real servant. And under the hood, the "real" dispatch function, _iceDispatch, calls dispatch for the dispatch interceptor servant. For real servants, ice_dispatch calls _iceDispatch. For example in Java:
default CompletionStage<OutputStream> ice_dispatch(Request request)
throws UserException
{
Incoming in = (Incoming)request;
in.startOver();
return _iceDispatch(in, in.getCurrent());
}
I propose to simplify all this by using a single dispatch method, ice_dispatch:
CompletionStage<OutputStream> ice_dispatch(Incoming request, Current current)
where the request parameter is a completely opaque type for the application, and current is provided as a separate parameter. This signature is more consistent with the method dispatch implemented by the application: these methods have a trailing Current parameter.
ice_dispatch would replace the existing dispatch/_iceDispatch/ice_dispatch, and a Dispatch interceptor would no longer be a separate class: any servant class that overrides ice_dispatch would be a dispatch interceptor. In particular, in C++ and Java, the application could override ice_dispatch in its servant class, and by doing so intercept dispatches. (With Ice 3.7, overriding ice_dispatch does not do anything, since Ice calls _iceDispatch, and ice_dispatch is just a wrapper that calls _iceDispatch).
Ice for Swift already uses this "single public dispatch method" model.
The retry support (in.startOver() in the Java snippet above) would move to the implementation of ice_dispatch in the generated code and a few built-in servants like Blobject and BlobjectAsync.
