Using readClassDescriptor() and maybe resolveClass() to permit Serialization versioning

Question

I am investigating different options in the Java Serialization mechanism to allow flexibility in our class structures for version-tolerant storage (and advocating for a diff

Answer 1

The problem is that readClassDescriptor is supposed to tell the ObjectInputStream how to read the data which is currently in the stream you are reading. if you look inside a serialized data stream, you will see that it not only stores the data, but lots of metadata about exactly what fields are present. this is what allows serialization to handle simple field additions/removals. however, when you override that method and discard the info returned from the stream, you are discarding the info about what fields are in the serialized data.

i think the solution to the problem would be to take the value returned by super.readClassDescriptor() and create a new class descriptor which returns the new class name, but otherwise returns the info from the old descriptor. (although, in looking at ObjectStreamField, it may be more complicated than that, but that is the general idea).