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From Justin Edelson <justinedel...@gmail.com>
Subject Re: [jr3] Plugin architecture
Date Thu, 18 Feb 2010 04:04:11 GMT

(Thanks for starting all these discussions...)

On 2/17/10 11:06 AM, Jukka Zitting wrote:
> Hi,
> Regardless of whether we go with a microkernel approach as discussed
> in the other thread, making Jackrabbit more modular and extensible
> would be quite useful. Besides the design benefits, plugin
> architectures typically also increase community participation as they
> make it easier to customize or extend the product.

> The current architecture already provides a number of extension points
> via various core interfaces and configuration points, but they are a
> bit cumbersome to use and not always in the points where you'd want
> them to be.

And... they're not part of the API.

> Here's what I have in mind for what we could do about
> this:
> * dynamic configuration: The current XML-based configuration mechanism
> needs to be updated whenever new extension points are introduced and
> makes it difficult to support dynamic plugin environments like OSGi or
> IoC containers.
> * higher level extension points: Most of our extension points are
> currently deep down at the bottom of the Jackrabbit architecture
> (PersistenceManager, Journal, FileSystem, SearchIndex, etc.). It would
> be useful to offer also higher level constructs like Repository and
> Session lifecycle listeners or transaction boundary checkers to be
> injected into the system.
> * whiteboard pattern: Instead of the custom context objects
> (PMContext, ClusterContext, etc.) and related init calls that
> statically wire our components together we should look at implementing
> more dynamic whiteboards from where all components could do on-demand
> lookups for the things they need.
> WDYT? Any other ideas on what we should do in this are?

Assuming this is done with OSGi, it'd be interesting to think about what
happens when core services (i.e. the PersistenceManager implementation)
get unregistered at runtime. Felix - have you looked at this in your
jackrabbit-bundle project?


> BR,
> Jukka Zitting

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