Concept
Jakarta Persistence API (JPA; formerly Java Persistence API) is a Jakarta EE application programming interface specification that describes the management of relational data in enterprise Java applications. Persistence in this context covers three areas: The API itself, defined in the jakarta.persistence package ( for Jakarta EE 8 and below) The Jakarta Persistence Query Language (JPQL; formerly Java Persistence Query Language) Object/relational metadata The reference implementation for JPA is EclipseLink. 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 Java EE 6 platform requires JPA 2.0). The JPA 2.1 specification was released 22 April 2013 (the Java EE 7 platform requires JPA 2.1). The JPA 2.2 specification was released in the summer of 2017. The JPA 3.1 specification, the latest version, was released in the spring of 2022 as part of Jakarta EE 10. A persistence entity is a lightweight Java class with its state 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 mapping (ORM) metadata. This metadata may be specified directly in the entity class file by using annotations or in a separate XML descriptor file distributed with the application. An example entity class with ORM metadata declared using annotations (import statements and setters/getters are omitted for simplicity). @Entity public class Person { @Id private long id; private String firstName; private String lastName; private int age; } The @Entity annotation declares that the class represents an entity. @Id declares the attribute which acts as the primary key of the entity. Additional annotations may be used to declare additional metadata (for example changing the default table name in the @Table annotation), or to create associations between entities.