+1 for making the return Map and returning
Collections.unmodifiableMap(allServices);
Thanks,
Keith.
On Wed, May 6, 2009 at 4:33 PM, Glen Daniels <g...@thoughtcraft.com> wrote:
> Amila Suriarachchi wrote:
> > Hm - it seems like you didn't actually get my point. We CAN'T
> > return the
> > actual allServices map because that would be breaking the abstraction
> > boundary provided by the class.
> >
> > As I remember this change was done to avoid concurrent modifications to
> > service map[1].
>
> Right - before this change we were doing something actively bad/wrong, i.e.
> returning the internal map. After the change we were returning a cloned
> copy
> of the map (though not using clone() for some reason), which is good in
> that
> it prevented people from misusing it.
>
> > At that time services map was a HashMap and could not fix the issue by
> > changing it to a ConcurrentHashMap since API method returns a HashMap.
> >
> > Currently anyone can get a copy of internal map (I think we can not use
> > clone() method since internal implementation is ConcurrentHashMap and we
> > need to return a HashMap). And if they want to add or remove service
> > they have to use addService and removeService respectively.
> >
> > Keith, if you really need the internal map IMHO best way is to add a new
> > API method.
>
> Ah, no. The "best way" is NOT TO OFFER ACCESS TO THE INTERNAL MAP.
>
> Keith's suggestion is to change the API so that it returns a Map - this
> would
> be much more correct since it increases the level of abstraction for the
> method, and would therefore let us, the implementors, freely decide how
> this
> should work internally. Right now we have problems because someone made
> this
> method overly specific, and this is what we should fix. (I was incorrect
> earlier when I said this wouldn't break people, btw - I was thinking about
> stuff like getServices().get("MyService"), but of course "HashMap foo =
> getServices()" would fail. I still think we should fix it.)
>
> My comment is that we should not only return a Map, we should change the
> implementation to make sure the Map is immutable, and make sure the JavaDoc
> explains what is going on.
>
> Make sense?
>
> --Glen
>
--
Keith Chapman
Senior Software Engineer
WSO2 Inc.
Oxygenating the Web Service Platform.
http://wso2.org/
blog: http://www.keith-chapman.org
