I would like to speed up startup time by serializing the Metadata and/or SessionFactory. I'm willing to mess with the code a bit to add Serializable, how realistic is this?

It's not very realistic. The SF might use a connection pool (e.g. C3P0, HikariCP), in which case those will not be serialized properly. Probably it's not an impossible task, but it's very tricky to make sure that all Hibernate Services are properly initialized after deserialization.

just serializing the metadata would avoid the connection pool problems right? I've been trying that and made some of the class loader related stuff, ClassLoaderDelegate, ClassLoaderService transient as it can be instantiated without deserialalization. also the JavaReflectionManager, but still getting unserializable exception on JavaXProperty, not sure what is trying to serialize it if the reflection manager is transient. I did t want to mess with hibernate Commons annotation

I managed to get it serializing and deserializing.. but you were dead on. it cannot find services in the registry even though they are there. any ideas?

I successfully got it working. Took some effort but i does serialize using a custom SessionFactoryBuilderFactory. I can do a PR if you guys are interested. Might needs a bit of cleaning up but in general it seems solid.

Sure. You can send the PR, thanks.

I posted a PR. I have filled out the CLA in the past for JBoss Rules. I tried making a JIRA account and logging in but failed..

Thanks, we will review it soon.