I'll synchronize the data from Google Contacts with a datastore in App Engine... i'm doing this in Python, and the datastore will be read later by a Java GAE instance.
Using Expando felt natural, but i'm not sure if the Java instance is going to be able to read it properly. If the answer is 'no, Java won't read it', what would be the optimal solution?
Edit: Once an Expando is compiled into a class file Java should be able to handle it... after all every Groovy object is an extension of the regular java Object class.
Check out this tutorial discussing mixing Groovy and Java for the gritty details.