[beanutils] Converters should really be final?

[Simon Kitching <sk...@apache.org>]

On Thu, 2005-05-26 at 04:41 +0200, bugzilla@apache.org wrote:
> Well, the change broke no unit tests, so I'm committing it.  All converter
> classes in the converters package have been made non-final.

I'm not entirely convinced this patch is a good idea.

When a class is final, there are no arguments about what methods/members
should be protected vs private. I bet now these classes are non-final
that we get bugzilla entries asking for methods/members to be made
protected or public :-)

When users can subclass a class, you must consider two things:
 * that removing protected methods/members is an incompatible change
 * that changing the internal logic to call protected methods in a
   different way (including not calling them at all) is an incompatible
   change, even though not a compile or link problem, as code that
   overrides the protected method will no longer work as expected.

As things currently stand, there are no protected members/methods in the
converter classes [1] so this isn't an issue. Well,
BooleanArrayConverter actually does have a protected member, though it
used to be a final class :-). So we should fix this to make it private,
yes?

And of course final classes are potentially faster than non-final ones.
Not really a major issue in beanutils given that it uses so much
reflection already but it's worth having if it doesn't do any harm.

So the question is what kind of gain there is from this change. How many
converters actually have enough logic in them that it is worth
subclassing them rather than implementing a custom converter from
scratch?

If BooleanConverter is the only converter with significant logic in id,
then maybe we would be better off enhancing BooleanConverter by adding a
constructor to take custom array of strings rather than allowing it to
be subclassed? Or maybe users could use the Decorator pattern rather
than subclassing to extend its functionality?

Regards,

Simon



---------------------------------------------------------------------
To unsubscribe, e-mail: commons-dev-unsubscribe@jakarta.apache.org
For additional commands, e-mail: commons-dev-help@jakarta.apache.org

Re: [beanutils] Converters should really be final?

[Simon Kitching <sk...@apache.org>]

On Thu, 2005-05-26 at 15:26 +1200, Simon Kitching wrote:
> If BooleanConverter is the only converter with significant logic in id,
> then maybe we would be better off enhancing BooleanConverter by adding a
> constructor to take custom array of strings rather than allowing it to
> be subclassed? Or maybe users could use the Decorator pattern rather
> than subclassing to extend its functionality?

Ahem .. BooleanConverter *was* enhanced a while ago (after the bugzilla
entry was created) to take an optional array of strings - by me. I
thought that class name was familiar :-). 

They say failing memory is a sign of old age - which I'm feeling acutely
at the moment as my birthday is less than a week away :-)

Cheers,

Simon



---------------------------------------------------------------------
To unsubscribe, e-mail: commons-dev-unsubscribe@jakarta.apache.org
For additional commands, e-mail: commons-dev-help@jakarta.apache.org