Vlad Mihalcea is a Java Champion and one of the top Hibernate ORM project committers. He created the Hypersistence Optimizer tool, which scans your application configuration and mappings and tells you what changes you need to make to speed up your data access layer.
He's been answering thousands of questions about Hibernate and JPA on StackOverflow, for which he's got gold badges for Hibernate, Java, and JPA tags.
Whenever he finds something interesting, he likes to share it on his personal blog. He believes in Open Source Software, and he thinks every developer should get involved, one way or the other.