Interacting with Databases through the Java Persistence API

The Java Persistence API (JPA) is an object relational mapping API. Object relational mapping tools help us automate mapping Java objects to relational database tables. Earlier versions of J2EE used Entity Beans as the standard approach for object relational mapping. Entity Beans attempted to keep the data in memory always synchronized with database data, a good idea in theory, however, in practice this feature resulted in poorly performing applications.