Google App Engine, JDO, and equals/hashCode

Question

I\'ve got an app in Google App Engine that was working fine. I realized that one on of my JDO-enhanced objects that I forgot to implement equals and hashCode (I need to use

Answer 1

I faced the same problem, and when I did the Project -> Clean, I saw following exception in the log:

{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/Administrator/workspace/Guestbook/war/WEB-INF/lib/datanucleus-appengine-1.0.8.final.jar" is already registered, and you are trying to register an identical plugin located at URL "file:/C:/eclipse/plugins/com.google.appengine.eclipse.sdkbundle.1.4.2_1.4.2.v201102111811/appengine-java-sdk-1.4.2/lib/user/orm/datanucleus-appengine-1.0.8.final.jar."}

So, I removed:

C:/Documents and Settings/Administrator/workspace/Guestbook/war/WEB-INF/lib/datanucleus-appengine-1.0.8.final.jar

from the eclipse project, cleaned and re-built, everything started working as expected.