Merging a blob on an entity results in a class cast exception

You can try to generalize, but you will end up with a lot of logic on TypeHelper that really should belong to the types themselves. From a design perspective it's much better to let the types act on UNFETCHED_PROPERTY.

For I added to org.hibernate.test.type.TypeTest but blobs, clobs and nclobs are not tested there.

In the future (6.0) this will likely change and we can re-evaluate then.

I posted something on the list regarding this issue: http://lists.jboss.org/pipermail/hibernate-dev/2018-May/017739.html .

Moving to 5.3.5 for now as it's not a regression. Will see if it can make it before that if all goes well.

I integrated the original test in the PR here: https://github.com/hibernate/hibernate-orm/pull/2390

We need to decide if we still want to keep the UNFETCHED_PROPERTY code in the types or get rid of it and use the other approach (or both).

Pushed to 5.3 branch as well.