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From Simon Nash <n...@apache.org>
Subject Re: Tuscany class loading (was: Re: Using EMF with Tuscany 1.6)
Date Wed, 28 Nov 2012 00:13:58 GMT
Millies, Sebastian wrote:
> Hello there,
> 
> I've never been back to talk about this, so here goes.
> 
> To re-iterate the problem: I want to set up my contributions, so that they can use
> different versions of third-party libraries than the Tuscany runtime. My original example
> was using recent versions of EMF (hence the subject line), another example is using
> Tuscany with an Apache Solr 4.0 backend, which requires different Apache Http Components.
> 
> The standard recommendation is [1], but I have had great trouble to get that to work.
(The
> reasons have to do with the use of SDOs in the application in question.)
> 
> I have therefore decided to try the opposite approach of  including any different versions
of components
> used  by Tuscany in nested jars in the contribution itself. Nested jars in a zip contributionget
added into
> the contribution classpath.
> 
> Here I am working under the assumption that the SCA contribution classloader would work
> somewhat like a webapp class loader in that it would not follow the delegation model,
> but would look for classes in the following order
> 1) inside the contribution
> 2) in the imports
> 3) in the parent classloader
> 
> With this behavior, everything goes well. For example, I can make calls to Apache Solr
through
> the solr-solrj-4.0.0.jar and its dependents, including httpclient-4.1.3.jar and httpcore-4.1.4.jar,
> without impacting HTTP calls made by Tuscany-generated proxies elsewhere.
> 
> Here's the snag: As it turned out, org.apache.tuscany.sca.contribution.java.impl.ContributionClassLoader
DID
> NOT work the way I expected, but rather looked in the parent classloader first, only
then inside the contribution.
> I had to change the coding (in module contribution-java) and the associated test. A patch
is attached.
> 
> Would my change break anything, perhaps with respect to OSGi? Is there anything in the
SCA spec that mandates a
> certain class loading behavior? I do feel that the alternative behavior is more natural
than the one that is currently
> implemented. (There a very few resources on Tuscany classloading, and e. g. [2] does
not seem to mention
> this particular issue.)
> 
> Unfortunately, I cannot get all the Tuscany 1.6  tests to compile and run with maven.
> 
> Please, would anyone be willing to see if Tuscany 1.6 with my patch applied would still
pass all current tests?
> (unless my proposal is obviously wrong for other reasons, of course)
> 
I can run these tests on the Tuscany 1.x trunk tomorrow.

   Simon

> Best,
> Sebastian
> 
> [2] https://cwiki.apache.org/TUSCANYWIKI/classloading.html
> 
> -----Ursprüngliche Nachricht-----
> Von: Simon Nash [mailto:nash@apache.org]
> Gesendet: Samstag, 25. August 2012 09:17
> An: user@tuscany.apache.org
> Betreff: Re: Using EMF with Tuscany 1.6
> 
> It's been over 2 years since I looked into this in detail and put together the list of
gudelines in [1], so I don't recall 100% of the detail of how this works.  See inline below
for my impressions of what may be happening.
> 
>  [cut]
> 
> I'll be interested to hear how you get on with that.
> 
>    Simon
> 
>> -- Sebastian
>>
>>> [1]
>>> http://mail-archives.apache.org/mod_mbox/tuscany-user/201006.mbox/%3C
>>> 4C164DD3.8090405@apache.org%3E
>>>
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