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From "thomas menzel" <dev.tom.men...@gmx.net>
Subject Re: [lang] propse new ObjectExistsException extends IllegalArgumentException
Date Mon, 14 Feb 2011 18:16:04 GMT
sure,

anywhere where u want to store objects and where u might not want to allow the addition of
"same" objects such as in registries, caches, collections.

often they are underpinned with internal sets or maps and at times it is better to signal
the client the hard way (ie. via a proper exception) that the object he intended to add already
exists.

the reason i want to have a distinct exception here, is to allow the client to catch this
case as opposed to the case where he might want to add an object who doest meet some constraints
and where i then throw a "normal" Illegal Argument Exception.

Also, there is sometimes the case that i will not add the object/key itself but rather a base
form that is then first converted into the real key/object.

such an exception would allow to return the derived key/object in a distinct way.
e.g

1. 
Regsitry.put(String url, Object){
 put(new Url(url, Object))
};

2. 
Regsitry.put(Url url, Object);


the implementation could throw a new ObjectExistException<Url>(url) in the 2nd method
and the client could get the id from T getObjectKey() and do some fall back work noit having
had the need to ever convert the string url himself into an Url Object.


hope that helps


-------- Original-Nachricht --------
> Datum: Fri, 11 Feb 2011 15:01:32 +0100
> Von: Simone Tripodi <simonetripodi@apache.org>
> An: Commons Developers List <dev@commons.apache.org>
> Betreff: Re: [lang] propse new ObjectExistsException extends IllegalArgumentException

> Hi Thomas,
> can you describe please in which non-JPA context the exception can
> become useful?
> Many thanks in advance, have a nice day,
> Simo
> 
> http://people.apache.org/~simonetripodi/
> http://www.99soft.org/
> 
> 
> 
> On Fri, Feb 11, 2011 at 10:31 AM, thomas menzel <dev.tom.menzel@gmx.net>
> wrote:
> > hi,
> >
> > i suggest a new exception under the commons.lang.exception namely
> >
> > ObjectExistsException extends IllegalArgumentException.
> >
> > in the jpa world there is already one like this, bit i think it has
> merit for also other cases outside of jpa and hence i would like to see it
> defined in apache's commons.lang.exception.
> >
> > what do u think?
> >
> > --
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