Sebastian Millies created TUSCANY-4073:
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Summary: Change classloader to use different versions of
third-party libraries than the Tuscany runtime
Key: TUSCANY-4073
URL: https://issues.apache.org/jira/browse/TUSCANY-4073
Project: Tuscany
Issue Type: Improvement
Components: SCA Java Runtime
Affects Versions: Java-SCA-1.6.2
Environment: Java 7 on Windows 7 (64bit)
Reporter: Sebastian Millies
Fix For: Java-SCA-1.6.2
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 contribution get 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)
Best,
Sebastian
[1]
http://mail-archives.apache.org/mod_mbox/tuscany-user/201006.mbox/%3c4c164dd3.8090...@apache.org%3E
[2] https://cwiki.apache.org/TUSCANYWIKI/classloading.html
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