This is being tracked in Issue 43 (
http://code.google.com/p/google-
gson/issues/detail?id=43). As well, the equivalent feature for
deserialization is being tracked in Issue 44 (
http://code.google.com/p/
google-gson/issues/detail?id=44).
We just released version 1.4 BETA, but we believe we can fix these
bugs without an API change; therefore, we will be targetting this with
the full 1.4 release.