Leo Simons wrote:
On Mon, 2002-11-25 at 13:49, Leo Sutic wrote:
Brief summary and my own thoughts:
The Context is used as a means to provide data to the component.
The Avalon docs say that "The context is the interface through which the
Component and it's Container communicate" but I think it has been shown
that any "active" operations can be better handled as Services, accessible
via a ServiceManager.
So, I'd like to specifically address the point of "what data".
My thoughts are this: The data is not a general Object-passing mechanism.
That is, the type of data being passed is limited. Every container, when it
deploys its components (be they servlets or maillets or whatever), sets up
a small block of data for it. That block of data can be, for web-servlets
the root URL for the servlet, activation time, or mail address for mailets.
The block can also contain the class loader in containers that do
classloader isolation.
Now, I'd say that the Context is the component's way of accessing that data
block and nothing more.
well put, I totally agree, sums it all up right there.
Now, what do we do with a component that used to run in a container
providing a ClassLoader in the context, that we're moving to a container
that does not practice CL isolation (and thus has no ClassLoader in the
context)? Possibilities:
1) Tough luck.
2) Define a minimum set of context entries that all containers must support.
I vote -0 for (1) and +1 for (2).
For the situation where we have a component that requires a context entry
that isn't provided by the container, and that didn't make it into the
minimum set of context entries, I'm +1 on (1). As long as we make it
crystal clear what context entries are container specific and what are
portable we shouldn't have any problem.
yep, where I should say we should not require something of containers
outside of the avalon project, just make it dead easy to do it the
recommended way ;D
some relevant stuff already going in this direction:
http://jakarta.apache.org/avalon/excalibur/info/context.html
http://jakarta.apache.org/avalon/excalibur/meta/context.html
http://jakarta.apache.org/avalon/phoenix/api/org/apache/avalon/phoenix/interfaces/ApplicationContext.html
http://jakarta.apache.org/avalon/phoenix/api/org/apache/avalon/phoenix/BlockContext.html
we actually were at a point where we had already been over the best way
to format the lookup string back in august, I think; can't find the docs
right now.
On formatting, the concensus as I seem to remember was :
<domain> ":" <key>
Which basically translates to:
avalon:home
avalon:work
merlin:something-special
phoenix:something-else
Cheers, Steve.
Regardless, a useful pattern is to store the lookup strings inside
something like org.apache.avalon.info.CommonContextKeys.class, so it
doesn't matter that much.
cheers,
- Leo
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Stephen J. McConnell
OSM SARL
digital products for a global economy
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