Hi All,
Hope all is well.
In our project I recently delved into the world of creating custom
markers specific for our particular application domain. I'd
thought that IoC/SoC was an excellent programming paradigm, and could
be applied to our application in a greater context, not just within
the standard avalon interfaces.
It turned out to be easy to begin with but difficult to finish, and
there seem to be lots of issues, at least to me :)
What I wanted to do was define a custom marker interface that would be
checked for each time a component was accessed (ie. during lookup()),
and have a method defined in that particular interface called each
time, appropriately.
The solution was to extend ECM's lookup() method in a subclass,
however the first problem I found was that most application code
specifies 'new ExcaliburComponentManager()' directly and needs to be
changed to use a derived class or made configurable to accept an
arbitrary component manager class, sometimes in several places
(eg. Cocoon, with my patch #8614 in bugzilla).
The other issue I realized later is ECS, select() also needs to be
extended, however this class incurs the same problem as ECM but more
often as selectors are specified in roles files and java code. It's
also more of an issue if a custom selector has already been written
(eg. Cocoon, with it's ExtendedComponentSelector).
So, subclassing doesn't seem to be the solution.
Another issue is that it seems to be quite difficult to insert a
custom marker mid-way into a component's startup/destruction phase.
I know this one won't come up as often as the others above, but as an
example Lief had this problem supporting the Instrumentable
marker interface.
I think we still need a way to ensure the defined order of the
standard avalon startup/destruction interfaces, but it could be
useful to include the ability to insert custom ones during
component startup (or should we consider the startup/destruction
process to be immutable ?).
I've taken a look at both the ECM/ECS and Fortress code, but both
don't seem to cover this space just yet (?). I'm looking for ideas
about how to add such functionality to our existing classes that
doesn't require excessive subclassing of handlers or component
managers.
Any ideas ? thoughts ?
I'm currently mulling over the thought of a potential solution that
involves modifying component handler/factories so that they can accept
a configurable startup/destruction sequence, but since I'm still an
avalon novice it would be great to hear comments/thoughts ? :)
Cheers,
Marcus
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,,$$$$$$$$$, Marcus Crafter
;$' '$$$$: Computer Systems Engineer
$: $$$$: ManageSoft GmbH
$ o_)$$$: 82-84 Mainzer Landstrasse
;$, _/\ &&:' 60327 Frankfurt Germany
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