OpenJPA is a 100% open-source implementation of the Java Persistence API (JPA), which is the persistence component for EJB in the Java EE 5 specification (part of JSR-220).

JPA combines the best ideas of other persintence technology, such as Hibernate, JDO and TopLink
 
The fields BLOB and CLOB of sql are translated for the Java programmer in the java.io.InputStream (for BLOBs) and java.io.Reader (for CLOBs) types, the objective of this project is to provide a serialization in database of these objects in a natural way.