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From Herve Quiroz <>
Subject [events] DynamicProxy decorator
Date Mon, 19 Apr 2004 19:00:51 GMT
Hi all,

I've realized that using standard decorator pattern usually makes the
"additional" interfaces such as "BoundedCollection" go away in the
process. This means for instance that the CollectionUtils.isFull()
method can no longer use the isFull() method from the object.

You can implement complex decorators to handle that but then each time
you add a new interface to your package, you have to re-implement your
decorators. This is quite not re-usable actually.

Lately, I've implemented an ObservableCollection decorator that is based
upon the dynamic proxy paradigm. With only a few lines of code, this
implementation allows the following:

Buffer buffer=new BoundedFifoBuffer();
ObservableCollection observable=ObservableCollectionUtil.decorate(buffer);

assert observable instanceof Buffer;
assert observable instanceof BoundedCollection;

..where there is no statement regarding Buffer and/or BoundedCollection
in the ObservableCollectionUtil source code.

I thought I could share.

I have the following available:

- interface ObservableCollection
- class ObservableCollectionUtil
- test case ObservableCollectionTest

So far, I have only one kind of event, CollectionIsNoLongerEmptyEvent,
as it is the only one I needed for my own package. However, if you feel
interested by my contribution, I can provide addtional events, or
refactor my classes to match one of the existing event models from

I also need observable functors for my own code, so chances are I will
implement them as well. Same goes here: if you're interested, please
tell me so we can plan things in advance and I don't need to refactor
the classes to donate them to Apache...

Tell me if you want to have a look at the classes, and I will post a
link on my homepage.


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