Thanks for your hint. Meanwhile I debugged the code and found the reason of the NullPointerException.
The method getObjectById is implemented by the class DatastoreJDOPersistenceManager. Within this method there is *EntityUtils.idToInternalKey(getObjectManager(), cls, key, false);*. This methods ends (obviously) in the class EntityUtils. Within this class and method you call *determineKind(cmd, om);*. But the parameter cmd is alrady null. A few methods later there is the follwoing line: *if (acmd.getTable() != null) {...}* et voila -> NullPointerException. The reason why acmd is null is because of this line within the EntityUtils class (method idToInternalKey): *AbstractClassMetaData cmd = om.getMetaDataManager().getMetaDataForClass(cls, om.getClassLoaderResolver());* Within the method getMetaDataForClass there is the following check: *if (isClassWithoutPersistenceInfo(c.getName())){ return null;}* So, does anybody know what this means? Yes - my entity class does not have any annotation but I thought this isn't necessary at all?! Should I have to include such kind of informations to my class? -- You received this message because you are subscribed to the Google Groups "Google App Engine for Java" group. To post to this group, send email to google-appengine-java@googlegroups.com. To unsubscribe from this group, send email to google-appengine-java+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-appengine-java?hl=en.