If you are Google App Engine, then the problem could be that even if you saved a java.util.HashSet<Long> to the datastore, it will give you back a org.datanucleus.sco.backed.HashSet<Long> when you retrieve the parent object. It's allowed, because the sco backed version is a subclass of java.util.HashSet. However, GWT cannot serialize a sco backed HashSet, and you get the error shown.
Solution - convert your sco backed HashSet to a java.util.HashSet on the server before sending back to the client. -- You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.
