EJB3 Persistence JPA JPA The Java Persistence API (JPA) is a specification from Sun Microsystems for the persistence of Java objects to any relational datastore. JPA requires J2SE 1.5 (also referred to as "Java 5") or higher, as it makes heavy use of new Java language features such as annotations and generics. This document provides an overview of JPA. Unless otherwise noted, the information presented applies to all JPA implementations. For coverage of OpenJPA's many extensions to the JPA specification, see the Reference Guide.

This document is intended for developers who want to learn about JPA in order to use it in their applications. It assumes that you have a strong knowledge of object-oriented concepts and Java, including Java 5 annotations and generics. It also assumes some experience with relational databases and the Structured Query Language (SQL).

lightweight persistence persistent data Persistent data is information that can outlive the program that creates it. The majority of complex programs use persistent data: GUI applications need to store user preferences across program invocations, web applications track user movements and orders over long periods of time, etc. Lightweight persistence is the storage and retrieval of persistent data with little or no work from you, the developer. For example, Java serialization serialization is a form of lightweight persistence because it can be used to persist Java objects directly to a file with very little effort. Serialization's capabilities as a lightweight persistence mechanism pale in comparison to those provided by JPA, however. The next chapter compares JPA to serialization and other available persistence mechanisms.