Hey guys:

Had a good talk w/ Dan and Lincoln at the conclusion of JBossWorld regarding wire compatibility and was asked to pass references along to this list.

The key is that marking a class as "implements Serializable" isn't sufficient to:

1) Make it really Serializable
2) Ensure that the wire protocol maintains compatibility across releases

I've been using a technique documented by Bob Lee awhile back:

http://crazybob.org/2006/01/unit-testing-serialization-evolution_13.html

The idea is that after you've formalized your protocol (ie. Externalizable or readObject/writeObject explicitly), you make a copy of this original class.  Then, using a special ObjectOutputStream, you can redefine this class as a new name, hence converting from old to new or new to old.

For instance, I implement this here in ShrinkWrap to make Archives Serializable:

http://anonsvn.jboss.org/repos/common/shrinkwrap/trunk/impl-base/src/test/java/org/jboss/shrinkwrap/impl/base/serialization/SerializationTestCase.java

Recommend this approach, or one similar.  Some folks like to serialize the original version into a .ser file which stays in SCM, and ends up being the basis for the test point.  But that can only test compat in one direction.

S,
ALR