Vlad Mihalcea is awesome! However, Hibernate, while helping in some use cases, in my opinion should not be the default solution one reaches for. It makes way too easy to do things in a way that works for a while and explodes later. And it is way too easy to be misunderstood, leading to performance and compositionality horrors. Still it is the only Java solution I know that manages to be reasonably portable between different DBMS.