Hibernate is an object-relational mapping (ORM) library for the Java language enabling developers to utilize POJO-style domain models in their applications in ways extending well beyond Object/Relational Mapping.
JDBI is an extension library over standard JDBC, to make writing relational database access more convenient (and correct!) from Java.
"Other useful pieces would be jdbi for database access much simpler than hibernate or other full orms async-httpclient for doing calls to other web services"
from question "Current core technologies for AJAX w/ Java?"