I'm looking for a technique or pattern to solve the following problem:
I have a class (TheClass) which needs to implement multiple interfaces (iA,
iB and iC). Each has a default implementation which is sufficient for my
needs (AImpl, BImpl and CImpl). In C++, you would use multiple inheritance
to solve this problem - inheriting from all three default implementations
in order to inherit all the default behavior. Of course, this is not
possible in Java (and frankly, I don't miss the complexity of multiple
inheritance).
In the past, I simply implement the interface and pass on method
calls to an aggregated class (e.g. AImpl). It's simple, but ugly.
I think this could be done with a dynamic proxy, but I'm concerned about
the performance of the heavy use of reflection. Some parts of our application
are extremely performance-sensitive. In my case, it is a compile-time
problem -- no run-time variability is required (in terms of the interfaces
implemented). So using reflection to direct every method call seems
like overkill.
From a language standpoint, it seems to me that some way of combining
the "implements" clause with a contained (aggregated) member would be
the ideal way to solve the problem. I think of it as
"hyper-aggregation". For example:
class TheClass implements iA, iB, iC
{
AImpl _myvarA provides iA = new AImpl();
AImpl _myvarB provides iB = new BImpl();
AImpl _myvarC provides iV = new CImpl();
}
Thus, the interface iA of AImpl would be exposed as the implementation
of iA for TheClass. Ideally, one would be able to override the
implementations of each interface within TheClass, when required.
In essence, it is an automatic usage of a dynamic proxy implemented
by the compiler. The method-call forwarding would be decided by
the compiler, rather than run-time reflection.
Assuming that I am not the first person to run into the problem (nor
the brightest), I have to ask how others solve this problem? Is there
some obvious problems with my solution above that has kept something
like this from being added to Java? I can't be the first person to
have thought of it.
TIA,
C
--
-------------------------------------------------------------------------
Chris Merrill | http://www.webperformanceinc.com
Web Performance Inc.
Website Load Testing and Stress Testing Software
-------------------------------------------------------------------------
_______________________________________________
Juglist mailing list
[email protected]
http://trijug.org/mailman/listinfo/juglist_trijug.org
