The context:
I am using Google App Engine along with Grails AppEngine plugin. At some point I started getting an exception when I was trying to start my development server. The only thing I had done before I got the error was- I had switched from App Engine SDK 1.2.5 to 1.2.8.
The solution
The problem is that the Grails clean command doesnt do a very good job of cleaning the cache folder when the App engine is installed.
The solution was to simply delete the cache folder created by cache and presto ! all was well again
The Exception
Caused by: org.datanucleus.exceptions.NucleusException: Plugin (Bundle) “org.datanucleus.store.appengine” is already registered. Ensure you dont have multiple JAR versions of the same plugin in the classpath. The URL “file:/C:/Documents%20and%20Settings/admin/.grails/1.1.1/projects/myapp/stage/WEB-INF/lib/datanucleus-appengine-1.0.3.jar” is already registered, and you are trying to register an identical plugin located at URL “file:/C:/Documents%20and%20Settings/admin/.grails/1.1.1/projects/myapp/stage/WEB-INF/lib/datanucleus-appengine-1.0.4.final.jar.”
at org.datanucleus.plugin.NonManagedPluginRegistry.registerBundle(NonManagedPluginRegistry.java:434)
at org.datanucleus.plugin.NonManagedPluginRegistry.registerBundle(NonManagedPluginRegistry.java:340)
at org.datanucleus.plugin.NonManagedPluginRegistry.registerExtensions(NonManagedPluginRegistry.java:222)
at org.datanucleus.plugin.NonManagedPluginRegistry.registerExtensionPoints(NonManagedPluginRegistry.java:153)
at org.datanucleus.plugin.PluginManager.registerExtensionPoints(PluginManager.java:82)
at org.datanucleus.OMFContext.<init>(OMFContext.java:160)
at org.datanucleus.enhancer.DataNucleusEnhancer.<init>(DataNucleusEnhancer.java:172)
at org.datanucleus.enhancer.DataNucleusEnhancer.<init>(DataNucleusEnhancer.java:150)
at org.datanucleus.enhancer.DataNucleusEnhancer.main(DataNucleusEnhancer.java:1157)
Versions:
Grails: 1.1.1
Goovy:1.6.2
Java: 1.5.x
App Engine SDK: 1.2.5
Grails App Engine Plugin : 0.8.5
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