I applied some changes to my junit test code in the pull request that shows that the attributeconverter is called in in both directions without taking the second level cache into account it seems. Hope that my expectation (and therefore the junit test) is not too stupid. This is what I currently see although I think my real problem is something else - maybe what you point me to.
I am still investigating. I wished there would be some way to get information from hibernate why and when it decides to do the conversions/update, a log setting or aop trick, something like this. If not only the entitys equals/hashCode methods are taken into account but also the entities properties equals/hashCode method this is something that I was not aware of.
Thank you so far!