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I'm creating a GWT app in Google App Engine, and using Google data store. Does anybody else have the problem of the DataNucleus being flakey as all get out?

I can save a class, and DataNucleus will do it's thing just fine. If I change ANYTHING in the class (even adding whitespace) and then save, I get the following error:

DataNucleus Enhancer completed with success for 0 classes. Timings : input=37 ms, enhance=0 ms, total=37 ms. Consult the log for full details DataNucleus Enhancer completed and no classes were enhanced. Consult the log for full details

Once I clean my project, DataNucleus is happy again.

Is this common when using eclipse? Is there a workaround?

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5 Answers

up vote 4 down vote accepted

The DataNucleus Enhancer is invoked by Google's Eclipse plugin. It is their plugin that causes the enhancement. The enhancer itself just does its job, enhancing the classes it is provided with. Nothing "flaky" about the enhancer ...

If you instead use the DataNucleus Eclipse plugin then you can do "on-demand" enhancement, enhancing just before deploy for example.

--Andy (DataNucleus)

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I have had a few similar experiences, and needed to clean the project as well. Its not all the time, but I think it happened once or twice a day, when I was regularly using Eclipse with the Google plugins.

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I was getting the error "Persistent class x does not seem to have been enhanced" and realized that I changed package names and the GAE plug in is set to enhance only certain classes.

You can change the list of classes that need enhancement in your project properties..Google...App Engine...ORM.

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Wow, it helps :) simple solution, thanks! –  Subtle Fox May 6 '13 at 9:41
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I had the same problem with the eclipse GAE plugin not "always" enhancing my classes so I installed the DataNucleus plugin to force it but I ran into a problem with the autogeneration of SerialVersionUIDs. I got an error saying "errors during build" but there were no compile errors. Uninstalled DataNucleus plugin and I was back to normal. They don't play well together, it seems.

I'm using GAE v1.3.3.1 and I installed DataNucleus eclipse plugin v2.0.2

Cleaning the project works, even if it's not the most elegant solution.

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I had the same problem. checking the log file on Eclipse get this message:

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:/Users/mmangar/projects/rga/google_sandbox/Sandbox/war/WEB-INF/lib/datanucleus-appengine-1.0.10.final.jar" is already registered, and you are trying to register an identical plugin located at URL "file:/opt/springsource-tool-suite-2.8.0.RELEASE-e3.7.1-macosx-carbon/springsource/sts-2.8.0.RELEASE/plugins/com.google.appengine.eclipse.sdkbundle_1.6.3.v201202290255r37/appengine-java-sdk-1.6.3/lib/user/orm/datanucleus-appengine-1.0.10.final.jar."

I had the same class trying to be loaded twice.

Removing one of the JAR file from my classpath it worked fine.

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