> -----Original Message-----
> From: Stephen McConnell [mailto:[EMAIL PROTECTED]
>
> I've just committed an example of embedding merlin so that you can get
> an idea of things (available in avalon/merlin/platform/tutorials/main).
I hope everyone has taken a look at this example:
http://cvs.apache.org/viewcvs.cgi/avalon/merlin/platform/tutorials/main/src/
java/tutorial/Main.java?rev=1.2&view=markup
Stephen shows a good example of just how simple it can be to start Merlin.
But, of course, that's not the *whole* story. In fact, I've told Stephen
before that I consider that approach cheating. :-) In this email I'm going
to try to give a better tour of the "magic" in merlin's startup process.
1. Several properties are set in the 'merlin.properties' file. This
includes telling merlin which block to run. To do this programmatically:
Factory factory = builder.getFactory();
Map criteria = factory.createDefaultCriteria();
criteria.put( "merlin.deployment", "conf/demo.block" );
factory.create( criteria );
(this was in Stephen's original version)
2. I'm guessing on this, but if you want to access the kernel, all you need
to do is change the above to:
Kernel merlin = (Kernel) factory.create(criteria);
You can then go about the business of accessing components via the
kernel.
But that's for a different email.
3. The repository does all the magic. Specifically, the repository gets all
the info to launch the merlin kernel from a META file:
http://www.ibiblio.org/maven/merlin/jars/merlin-impl-3.3-SNAPSHOT.jar.meta
This file accurately shows you what dependencies are required (three
classloaders and 22 jars). It also reveals the next trick.
4. org.apache.avalon.merlin.impl.DefaultFactory does all the work.
If you want to *really* see how Merlin starts up, look at this class.
Now, I like the repository idea. In fact, it's the primary reason I decided
to use Merlin in one of my latest apps. However, there are other times when
I don't really want to use a repository. In fact, sometimes I want to be
able to deliver a single large jar file that includes everything I need.
With that in mind, I decided to look at how I could start up Merlin
_without_ using the repository. So I started with the DefaultKernel class
and started tracing back all the dependencies I would need. I only
considered constructor dependencies, just the bare minimum I would need to
full fill the requirements of the DefaultKernel.
Result? 30+ classes required. And you still need a Repository class. A
simple list of the dependencies has been attached for those who are
interested.
I had done something similar with Merlin but that was before the whole
Repository package. After reviewing it now I see that there isn't any easy
way to start up Merlin without a repository and without a bit of meta-info.
That's not necessarily a bad thing -- ECM and Fortress generally require
external configuration files and a few helper/factory classes.
So in the end, I'm not necessarily encouraged or discouraged. I've been
thinking about a number of ways we could make Merlin simpler and give users
more options on how to start Merlin and load/deploy their components. My
goal is to decrease the learning curve of Avalon so that a new user could
get the basics down within an hour. That involves not only better
documentation but also a very simple way to work with the container.
Thoughts?
J. Aaron Farr
SONY ELECTRONICS
DDP-CIM
(724) 696-7653
Kernel
KernelContext
Logger
ContainmentModel
ContaintmentContext
Logger
SystemContext
ClassloaderModel
ContainmentProfile
SystemContext
LoggerManager
LoggingDescriptor
CategoryDirective
TargetDescriptor
FileTargetProvider
Repository
CacheManager
ProxyContext
ClassLoaderModel
ClassLoaderContext
Logger
Repository (another)
ClassLoaderDirective
LibraryDirective
ClasspathDirective
FilesetDirective
RepositoryDirective
ResourceDirective
ContainmentPrifile
ClassloaderDirective (another)
ServiceDirective
ServiceDescriptor
ReferenceDescriptor
CategoriesDirective
Profile (which one???)
BlockCompositionProfile
or
DeploymentProfile
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