Yannick Menager wrote:
I have been working on some apps that have require a plugin infrastructure.
However merlin doesn't really handle that kind of things very nicely. First there's the lack of selector that already has been discussed, but more, classloading needs to be manually edited to include blocks which might contain such service implementations.
Classloader definitions can be programatically modified by this is complex territory. If (and there is a very big if here) you need to expand a classloader (as opposed to branching a classloader) then you basically have to take the classloader down (which means taking down all of the components and suspending all consumers), modify the classloader metamodel, revalidate and redeploy the classloader, and all of the components. On the otherhand - if the API of the components you want to plug in are already in the classloader - then you talking about branching which is comparitvely drop dead easy (just add a block to the block you want to plug in to - this will result in a new classloader branch automatically).
What I was thinking, is that it would be nice to implement a functionality where a module could actually request all services X, without indicating the classloading dependencies. Of course in order to do that, merlin would need to have a cache index of which jars contains which services, and then use that to provide the service requestor with a list of available implementations.
This is what the block defintion provides this - it *is* the persistent defintion of the classloader dependencies for a particular deployment scanario.
What do you guys think ?
I think I need a more complete picture of the definition of plugin (that you have in mind) and how this differs from the plugging in of a block as a child of another block.
Cheers, Steve.
If there is a strong interest on that, I just might implement it.
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