The Java Persistence API, sometimes referred to as JPA, is a Java programming language application programming interface specification which describes the management of relational data in applications using Java Platform, Standard Edition and Java Platform, Enterprise Edition.
The Java Persistence API originated as part of the work of the JSR 220 Expert Group of the Java Community Process. JPA 2.0 was the work of the JSR 317 Expert Group.
Persistence in this context covers three areas:
- the API itself, defined in the
javax.persistencepackage - the Java Persistence Query Language (JPQL)
- object/relational metadata
History
The final release date of the JPA 1.0 specification was 11 May 2006 as part of Java Community Process JSR 220. The JPA 2.0 specification was released 10 December 2009. The JPA 2.1 specification was released 22 April 2013.
Entities
A persistence entity is a lightweight Java class whose state is typically persisted to a table in a relational database. Instances of such an entity correspond to individual rows in the table. Entities typically have relationships with other entities, and these relationships are expressed through object/relational metadata. Object/relational metadata can be specified directly in the entity class file by using annotations, or in a separate XML descriptor file distributed with the application.
The Java Persistence Query Language
The Java Persistence Query Language (JPQL) makes queries against entities stored in a relational database. Queries resemble SQL queries in syntax, but operate against entity objects rather than directly with database tables.
Hibernate provides an open source object-relational mapping framework for Java. Versions 3.2 and later provide an implementation for the Java Persistence API. Gavin King founded the Hibernate project. He representedJBoss on JSR 220, the JCP expert group charged with developing JPA. This led to ongoing controversy and speculation surrounding the relationship between JPA and Hibernate. Sun Microsystems has stated that ideas came from several frameworks, including Hibernate and Java Data Objects (JDO).