[2.0] LinkageError: loader constraint violation

[Leone]

I was playing with this project https://github.com/bjartek/computer-database-mongo in Play 2.0.1 and every time it recompiles I get the error attatched in the next reload.

Do you have any idea what is going on?

Thanks.

[Andy Czerwonka]

So I'm not the only one.

https://groups.google.com/forum/m/#!topic/play-framework/9eWxRByjjQU

[Andy Czerwonka]

Are you saying its happening to you on the vanilla project? No changes?

[Leone]

Yes. It's happening on the vanilla project. Every time I try to edit the Computer model. There is a Page helper object and the error rise in view. I don't know what's going on.

[Leone]

After deleting ALL ivy and maven related directories (~/.ivi2, ~/.m2, PLAY_HOME/repository/cache and PLAY_HOME/repository/local), I'm getting this error.

Em domingo, 13 de maio de 2012 11h17min07s UTC-3, Andy Czerwonka escreveu:

[Andy Czerwonka]

It would be awesome to get some feedback from the Play team as we're not sure how to deal with this issue. I am having the same problem. I assume it's a bug, but I don't know.

[Leone]

It is related to Salat caching mechanism. Look at this blog post describing the problem: http://ska-la.blogspot.com.br/2012/03/play-20-and-salat-mongodb-dao-provider.html?showComment=1337091263187#c7254048190252210297

Play team is aware about this error: https://play.lighthouseapp.com/projects/82401/tickets/216-play-scala-20-recompilation-problem-using-salat#ticket-216-7
and they provided a workaround: https://github.com/andypetrella/classloading-problem

[Guillaume Bort]

Anyway there is nothing we can do on the Play side. To be able to
reload your code, everything must be fully stateless. If any lib try
to keep reference on old classLoader/classes it will lead to
ClassCastException/LinkageError problems.

The only solution is to have a proper Salat plugin for Play 2.0 that
take care to clean all the dirty Salat cache on application reloading.

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Guillaume Bort

[Andy Czerwonka]

I'm not sure how this interacts with the latest Salat plugin - 1.0.3. I tried the approach used in https://github.com/andypetrella/classloading-problem and it messes with the persistence in that it wraps each object. For example, without the implicit salatctx saving a user object gives me the following:

{ "_id" : ObjectId("4fb586b7ccf2ddffeb898b87"), "username" : "aczerwonka", "email" : "andycz...@myemail.com" }

That's what I expect. When I search by username, I find the right version and everything is great. But, when I import the implicit salatctx, the same operation results in:

{ "_id" : ObjectId("4fb58a3dccf268cf9d43720e"), "_typeHint" : "models.User", "id" : ObjectId("4fb58a2fccf268cf9d43720c"), "username" : "aczerwonka", "email" : "andycz...@myemail.com" }

This is not what I expect. My findByUsername obviously fails and I end up creating many User objects in the mongo database. I'm not sure what is happening the the implicit salatctx magic is magically messing up everything.

git revert :-(

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