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From David Jencks <david_jen...@yahoo.com>
Subject Re: Features and OBR
Date Fri, 02 Jul 2010 16:34:03 GMT

On Jul 2, 2010, at 8:03 AM, Guillaume Nodet wrote:

> I've just added support for pluggable resolvers for features.
> I've also created an OBR based resolver that is installed with the obr feature.
> 
> Now you can do the following:
> 
>  <feature name="xx" version="yy" resolver="obr">
>      <bundle>bundle:(&(symbolicname=org.apache.camel.camel-blueprint)(version>=2.4.0)(version<2.4.1))</bundle>
>  </feature>
> 
> If OBR has been configured with the needed repositories, it will
> install camel-blueprint bundle with all the required dependencies.
> The benefit is that you don't have to specify all the dependencies,
> but only the key bundles.  The added benefit is that the deployment
> will leverage what is already installed and you don't have to maintain
> an homogeneous set of repositories (for example, you should not have
> to specify which version of spring you want to use and obr will reuse
> the one installed if possible, or choose which one to install based on
> the constraints expressed by the bundles).
> 
> I haven't updated the feature descriptor yet, mostly because we don't
> have a obr repository which contain all the bundles we need.
> I have one locally that contain all the bundles present on maven
> central, but it's a bit too big to be used in this context, so not
> sure how to handle that yet.
> 
> Anyway, just wanted to give a heads up on that.


One of the points of friction I see between maven and osgi is that in maven you explicitly
 specify which artifacts supply your needed dependencies whereas in osgi they magically appear
from something like OBR.  I've always wondered where the OBR-like info is supposed to come
from.  On the other hand, if you are using maven to build, you have a reasonable set of candidate
artifacts in the maven dependencies (assuming they are all bundles).

Something I started experimenting with in geronimo is to, for each feature, construct an OBR
xml file out of the maven dependencies.  Just before you try to install the feature, you add
the obr fragment to the OBR instance you are using for resolving the feature.  This pretty
much assures that something that will enable the bundles in the features to resolve will be
available.  

Writing the code for this was easy, but we weren't relying enough on OBR at the time to find
out how well it works in practice.  I have been wondering if anyone else would think this
is a reasonable approach to investigate.

thanks
david jencks 
> 
> -- 
> Cheers,
> Guillaume Nodet
> ------------------------
> Blog: http://gnodet.blogspot.com/
> ------------------------
> Open Source SOA
> http://fusesource.com


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