Wednesday, March 16, 2011

Grails - Excluding plugin dependencies from war

I started using maven to build my Grails project, and upgraded Grails to version 1.3.7. Running mvn grails:run-app with Tomcat works fine, but when I tried to generate a war file with mvn package, and deploy that to Jetty, it failed:

Exception in thread "main" java.lang.IllegalAccessError: tried to access field
org.slf4j.impl.StaticLoggerBinder.SINGLETON from class org.slf4j.LoggerFactory
at org.slf4j.LoggerFactory.<clinit>(LoggerFactory.java:60)

Googling led me to the SLF4J FAQ (http://www.slf4j.org/faq.html) which says that this is caused by slf4j-api <= 1.5.5 being incompatible with an slf4j binding > 1.5.5. My application declares slf4j-api 1.5.8 and slf4j-log4j12 1.5.8 as dependencies. Running mvn dependency:tree didn't reveal any slf4j-api <= 1.5.5, but, indeed, in WEB-INF/lib in the application's war-file there was a slf4j-api-1.5.2.jar. Where did it come from?

When running mvn package with the log level of Ivy resolver set to "info", it seems that it was pulled in by Hibernate, through its dependencies hibernate-core and hibernate-commons-annotations. Problem solved! Grails has great support for determining which of the plugin's dependencies to exclude. In the Grails Reference Documentation it says:

If a plugin is using a JAR which conflicts with another plugin, or an application dependency then you can override how a plugin resolves its dependencies inside an application using exclusions. For example:

plugins {
   runtime( "org.grails.plugins:hibernate:1.3.0" ) {
     excludes "javassist"
   }
}

This means that all I have to do is include the following in my BuildConfig.groovy:

runtime("org.grails.plugins:hibernate:1.3.7") {
  excludes "slf4j-api"
}

No luck. slf4j-api-1.5.2.jar was still there. Googling suggested that there is a bug in Grails that prevents it from excluding transitive dependencies of plugins (GRAILS-6910). Allright. Let me exclude hibernate-core and hibernate-comons-annotations, then, and include them as dependencies with slf4j-api excluded, ie.

dependencies {
  compile("org.hibernate:hibernate-commons-annotations:3.1.0.GA") {
    excludes "slf4j-api"
  }
  compile("org.hibernate:hibernate-core:3.1.0.GA") {
    excludes "slf4j-api"
  }
}

plugins {
  runtime("org.grails.plugins:hibernate:1.3.7") {
    excludes "hibernate-core", "hibernate-commons-annotations"
  }
}

Still no luck.

Finally, Google led me to this page: Excluding files from a WAR with Grails – the right way. There, Marc Palmer suggested adding the following to Config.groovy to exclude a certain .jar-file from the war file:



grails.war.resources = { stagingDir ->
  delete(file:"${stagingDir}/WEB-INF/lib/slf4j-api-1.5.2.jar")
}

Ran mvn package while I held my breath. Once finished, I checked the generated war file, and, to my disappointment, the slf4j-api-1.5.2.jar was still there.

However, reading through the mentioned post's comments, some guy suggested that it should be added to BuildConfig.groovy, rather than Config.groovy.


Tried that. And finally, no slf4j-api-1.5.2.jar in the generated war file, only my own slf4j-api-1.5.8.jar.

Deployed the war to Jetty, and it worked like a charm.

It seems to me that Grails' dependency manipulation methods are rather buggy at the moment. I find this an acceptable workaround.

13 comments:

  1. Thanks, this really helped.
    Upgrading grails is always 'fun'...

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  2. Yes, it is. Glad you found the post helpful.

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  3. thank you thank you thank you. :)

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  4. I have gone through exact same steps with a brand new app running grails 1.3.7, and have come to the identical conclusion as you!

    DB.

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  5. You rock man - Same exact SLF4J headache, here. We had new Grails project in existing Maven environment. This has held up project deploy in integration for a few days!

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  6. This is good news that it works, however; the design seems rather hacky, doesn’t it? Adding a layer of excludes? Ewww.

    The correct behavior for Maven should be to build and consult a superseding dependency graph in the build, no? Like if Hibernate is asking for slf4j version 1.5.2, Maven should look for other artifacts that need slf4j, if one needs a newer one, don’t load the older one, instead maybe print out a warning and at least try to let the newest one provide the dependency for both.

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  7. If you want to dig further into this, have a look into the Grails sources where a check on a closure for grails.war.resources is done:
    grails/scripts/_GrailsWar.groovy

    if (buildConfig.grails.war.resources instanceof Closure) { // here the closure will be called}

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  8. This comment has been removed by the author.

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  9. Thx very usefull since I've been working with an old grails version and a boilerplate of grails/ivy and maven integration dependencies management... You saved me a lot of deployment errors...

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  10. I tried: plugins {
    runtime(':hibernate:3.6.10.10')
    { excludes 'javassist','hibernate-core', 'hibernate-commons-annotations' }
    getting error/warning:
    method [runtime] in grails-app/conf/BuildConfig.groovy doesn't exist. Ignoring.

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    Replies
    1. That looks like another issue and would be hard to figure out without more information. Have you tried stackoverflow.com?

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