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From Sylvain Wallez <sylv...@apache.org>
Subject Re: [FYI] Eclipse moving to OSGi
Date Mon, 01 Dec 2003 21:26:25 GMT
Berin Loritsch wrote:

> Sylvain Wallez wrote:
>> Hi all,
>> I just found that Eclipse is moving their component container to OSGi 
>> [1]. Avalon was one of the possible candidates, but it seems that 
>> only OSGi was seriously considered [2].
>> OSGi was up to now mostly used in embedded systems (cars, 
>> automation), and its adoption by the Eclipse team will promote this 
>> platform to many more developpers, particularly in the J2EE world. 
>> I'm wondering [3] how this can impact the future of Avalon.
>> What do you think?
> My initial look at OSGi is that it is solving a different set of 
> problems than Avalon.  Although with some of the work being done on 
> the Avalon repository, that may be different now.
> My perception was that OSGi was working with the JAR==component 
> outlook, and had some nice features for loading and unloading these 
> JARs.  Avalon OTOH, was working with smaller granularity components.  
> So, in one sense, they can work together.  In fact, it might be a good 
> marriage.

And OSGi "bundle" (that's the term for the deployment unit) can provide 
several services: a "BundleActivator" class inside the bundle registers 
the provided services (there can be several) when the bundle is loaded. 
Registering a service consists in registering an instance of the service 
interface with additionnal properties that describe the service. The 
lookup mechanism then allows to select a particular implementation of 
the service depending on property values, by using a simple LDAP-like 
query language.

OSGi is also very good a loading/downloading/unloading bundles.

I have the impression OSGi directly compares to Phoenix blocks (don't 
know about Merlin?), but it doesn't support non-singleton services like 
ECM or Fortress.

You can have a quick look at how it works through the very explanatory 
tutorial at http://oscar-osgi.sourceforge.net/tutorial/index.html


Sylvain Wallez                                  Anyware Technologies
http://www.apache.org/~sylvain           http://www.anyware-tech.com
{ XML, Java, Cocoon, OpenSource }*{ Training, Consulting, Projects }
Orixo, the opensource XML business alliance  -  http://www.orixo.com

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