In gwt-dispatch, Action and Result classes extend java.io.Serializable; however, I have bumped up against this error a few times:
Type 'com.your_company...' was not included in the set of types which can be serialized by this SerializationPolicy or its Class object could not be loaded.
I get this error for one of two reasons, and wanted it on my blog so I can search it next time 🙂
1. I forgot to include a no-arg constructor.
2. The type of one or more class fields in the Action or Result class is not Serializable (usually a domain object for which I’ve forgotten to implement Serializable).
As a last resort, delete the *.gwt.rpc files in your war/app directory, clean and rebuild. But the problem is usually one of the above…
