java Google AppEngine Eclipse:ormLibs不能为空

Question

我目前正在尝试使用Google App Engine的PersistentManagerFactory持久化一个类的对象。我犯了一个我不太明白的错误：

 org.datanucleus.api.jdo.exceptions.ClassNotPersistenceCapableException: 
 The class "com.google.gwt.sample.vendorcouver.client.user.VenUser" is not persistable. 
 This means that it either hasnt been enhanced, or that the enhanced version of the file 
 is not in the CLASSPATH (or is hidden by an unenhanced version), or the Meta-
 Data/annotations for the class are not found.

我在Why do I get ClassNotPersistableException while running GWT App Engine application in hosted mode?做了所有建议（确保我在类中有@PersistenceCapable，确保我的类路径中没有任何重复的.jar）。最终，我在Datanucleus增强控制台中发现：

 java.lang.NullPointerException: ormLibs cannot be null
at com.google.appengine.tools.enhancer.EnhancerLoader.removeOrmLibs(EnhancerLoader.java:66)
at      com.google.appengine.tools.enhancer.EnhancerLoader.getClassPath(EnhancerLoader.java:43)
at com.google.appengine.tools.enhancer.EnhancerLoader.<init>(EnhancerLoader.java:37)
at com.google.appengine.tools.enhancer.Enhancer.execute(Enhancer.java:69)
at com.google.appengine.tools.enhancer.Enhance.<init>(Enhance.java:71)
at com.google.appengine.tools.enhancer.Enhance.main(Enhance.java:51)

我不完全确定ormLibs应该是什么，而且我似乎在网上找不到太多关于它的信息。任何帮助都将不胜感激