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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 10:12:32 GMT
Simon Nash wrote:
> 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
I tried this and got the following failures in modules and samples:












I didn't go any further, as the above errors seem to indicate there
are serious issues with this change.


>> 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
>> IDS Scheer Consulting GmbH
>> Geschäftsführer/Managing Directors: Michael Rehm, Ivo Totev
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