[news.eclipse.technology.m2e] Re: Eclipse errors after SCM update

[Igor Fedorenko <igor@xxxxxxxxxxxxxx>]

See my comments inline

Yves Schumann wrote:
> Hello
>
> After migrating an application from Ant build to Maven build I ran
> into some problems. The original application consists of around 20
> eclipse projects from which Ant creates three *.war files, so three 
> webapplications. The amount of functionality of these application
> should be increased a lot in the next time but there are a lot of
> problems with Ant, so we decide to migrate the projects to use Maven.
> That's the history. ;-)
>
> After a lot of cleanup and migration work these projects were split
> up into around the double amount of eclipse projects using m2e. 
> Additionally I've created a plain project which is only used for 
> configuration, i. e. profiles, dependency management a.s.o. This 
> configuration project is referenced from nearly all other projects as
>  parent project. Maybe this is not the final solution but currently
> this setup works fine using plain Maven.
>
> The problems begin with m2e and our development behaviour.
> Development is done feature based which means, that we have different
> branches on our SCM (which is ClearCase) for each feature. After a
> lot of tests (like integration tests, system tests, ...) these
> branches are merged into the release branch. Additionally some of
> these feature branches were merged together in both directions every
> two or three days, because they require each other but development
> can't be done on one branch. Currently not the best solution but I'm
> not in the position to change this. Maybe it can be done step by
> step...
>
> One of the major problems for us is, that after an update from SCM 
> Eclipse shows a huge amount of resolving errors but maven build runs 
> successfully through without any errors. Additionally confusing the 
> fact, that this happens mostly on different developers but not all of
>  them!? After digging into possible solutions I've modified "Goals to
>  invoke after project clean" on every project and entered "clean
> compile test-compile" there. But this helps not really during or
> after an update out of SCM, the errors mostly still there on Eclipse,
> even after running Eclipse clean.
>
> Now I'm uninspired what to do. :-/ One guess is that this has to do
> with Eclipse's own history inside the workspace metadata. Does anyone
> know how to clear this history? This history is growing over time but
> in my or our case not really necessary because everything is under
> version control.


I don't have much experience with Eclipse ClearCase plugin (and the
little experience I had was not a good one), so I can only give you some
hints how you can start troubleshooting this problem but to solution. I
assume you're talking about Maven dependency resolution problems. If you
are talking about Java compilation errors, then most likely these
suggestions do not apply.

First, make sure that Eclipse workspace is in sync with underlying
filesystem (select all projects, right click, Refresh).

If Refresh does not help, try forcing Maven dependency re-resolution
(Project->Update All Maven Dependencies). Internally, m2e uses
filesystem timestamps to detect pom.xml file changes and it may get
confused if ClearCase does anything funny.

You can also try full/clean workspace build (Project->Clean...->Clean
all projects).

And lastly, 0.9.6 is quite old so I would recommend giving 0.9.8 a try.

If any of these steps makes the errors go away, we can dig deeper to see
how to actually fix the problem.


> Oh, there is another thing I can mention here: Eclipse hangs without
> any reaction if I try to import a lot of projects at once. Nothing
> happens and the percentage counter "Updating Maven Dependencies" on
> the bottom of the screen freezes. So the creation of a new workspace
> is very sad because with one import step only a small amount of
> projects can be importet. It works best for us, if with every import
> step only three or four projects are imported. The import is done
> using the default Eclipse project importer. The Maven project
> importer can't be used because it shut down Eclipse completely
> sometimes/often. Otherwise the behaviour is the same as described
> above.

This is likely https://bugs.eclipse.org/bugs/show_bug.cgi?id=249930.
It is not m2e specific. You can either build patched JDT core or move
to Eclipse 3.5.

> All this is done with installed JRE/JDK 6u12, Eclipse 3.4.2 
> (M20090111-1700) and m2e 0.9.6 because 0.9.7 has a problem with the 
> creation of web projects (If I remember right something with the 
> creation/compression of the *.war file). If this is solved I can try
> an update but this a definitive requirement for our developers and
> the reason to stay on 0.9.6. Please let me know if I can (or should)
> try an update of separate m2e components, but the build of web
> projects is a must for us at the moment.
>
> Wow, a lot of text! Would be nice if someone can read it and possibly
>  give me a hint. Thx a lot in advance.
>
> Regards, Yves