Re: [cross-project-issues-dev] Jars in jars is good citicenship?

[Ed Merks <merks@xxxxxxxxxx>]

Thomas,

It seems to me we've run into this kind of issue too with
org.eclipse.emf.ant where org.eclipse.uml2.uml.ecore.importer extends those
tasks and while the build worked fine in the development environment, the
PDE build building UML2 against the packaged build result of EMF has
problems.  I think we needed to hack the build to unjar the plugin; or
maybe we did something worse.  I've never consider what impact this had on
other clients who might want to extend our tasks...

I've certainly been frustrated that
https://bugs.eclipse.org/bugs/show_bug.cgi?id=109137 never gets addressed
because JDT needs to address
https://bugs.eclipse.org/bugs/show_bug.cgi?id=182537 which can't be done
without some kind of hooks in the Resource implementation, and that never
gets done for a reason I can no longer remember.  I'm not really sure why
your particular issue couldn't be addressed given that installed jarred
plugins with nested jars are often exploded and then the nested jar is
available directly in the file system.  I suppose this is naive thinking in
that this applies only if the jar is actually the one in the running
environment itself.  In your case, are the non-Ant classes jarred up in a
different jar that is also a nested jar in the jar?  In our case, we really
have to jar the plugin or we get stuck with the problem I just mentioned.
I suppose we could have not jarred the plugin and produced two jars too,
but we didn't recognize the problem with the Ant jar until longer after we
made the choice....

It seems to me if the compiler issue can't be fixed, we'd need to at least
consider making exceptions...


Ed Merks/Toronto/IBM@IBMCA
mailto: merks@xxxxxxxxxx
905-413-3265  (t/l 313)




                                                                           
             Thomas Hallgren                                               
             <thomas@xxxxxxx>                                              
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             11/02/2007 06:52                                      Subject 
             AM                        [cross-project-issues-dev] Jars in  
                                       jars is good citicenship?           
                                                                           
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I have a question regarding the "Should Do item #1 "Projects should have
jar'ed plug-ins because this is good Eclipse citizenship"

I think this creates problems for downstream projects that have
dependencies on these jars when the plug-ins themselves contains other
jars. The eclipse runtime can handle this but the compiler can't. Here's
a use case (using a component that is not part of Ganymede, but anyway)
that highlights this.

I'm developing the Subclipse plug-in for Buckminster. It is dependent on
the org.tigris.subversion.subclipse.core. This plug-in is only available
as a jar'ed plug-in that in turn contains other jars and this is the
cause for some headache.

I have it installed in my IDE (or in my target platform) but I still get
compilation errors. The remedy is to import the plugin into my
workspace. When I do that, and the compiler errors disappear.
Unfortunately, now I break the self-hosting instead. So I need to
handcraft the bundle selection in my launcher and specify that this
bundle must be picked from the target platform rather then from my
workspace. Now everything works fine.

I've been told that since all jars that are needed are available as OSGi
bundles in Orbit, this problem doesn't exist. No jars in jars construct
is ever needed. I think there are exceptions to that rule. A bundle that
provides Ant tasks for instance, needs to keep them separate from what's
seen by the bundle classloader and hence, must use the jars in jars
mechanism. Perhaps there are other cases that I'm not aware of.

My point is, perhaps "Should Do item #1" should be changed to "Projects
that doesn't produce plug-ins that themselves contain jars should have
jar'ed plug-ins because this is good Eclipse citizenship"?

Regards,
Thomas Hallgren

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