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Java Persistence API (JPA) - A Brief Overview
The document provides an overview of the Java Persistence API (JPA) and its evolution from previous Java application persistence methods. It highlights JPA's ease of use, features such as non-intrusiveness, POJO persistence, and the use of JPQL for queries, along with characteristics of entities that must be persistable and uniquely identifiable. The document also discusses JPA's independence from the EJB specification and its future as a standalone JSR.
Java Persistence API (JPA) - A Brief Overview
- 1. Java Persistence API(JPA) A Brief Overview By Scott Rabon
- 2. We have comea long way • Java application persistence history – JDBC – EJB Entity Beans 1
- 3. Industry answered thecall • Proprietary persistence products were introduced – JBoss Hibernate – Oracle Top Link 2
- 4. Why Another Standard •Standard goes deeper than a product • Can be implemented by different vendors • Developers code to interface, not implementation 3
- 5. A Standard IsBorn JSR 220 – EJB 3.0 Specification Java Persistence API part of EJB 3.0 Specification 4
- 6. JPA Fun Facts •JSR 220 formed May 2003 • Released May 2006 • Expert group consisted of industry ORM developers 5
- 7. JPA – Designedfor Ease of Use • Main goal of design team • Elegant, powerful and flexible • Easy to learn 6
- 8. Aspects: POJO Persistence •Objects are POJO’s • Mapping is metadata driven • External XML or annotation based 7
- 9. Aspects: Non Intrusiveness •API does not intrude on objects • API exists as a separate layer from persistent objects • Objects are “unaware” of the API 8
- 10. Aspects: Object Queries •Query across entities and relationships • Expressed in Java Persistence Query Language (JPQL) • Uses a schema abstraction 9
- 11. Aspects: Mobile Entities •Detachment Model • Move entities between JVM’s • Can change state anywhere along the way • Reattach upon return 10
- 12. Aspects: Simple Configuration •Java SE 5 Annotations • XML • Heavy use of defaults 11
- 13. Aspects: Integration andTestability • Challenge: Testing on an app server • API works outside application server – Two tier apps – Unit tests and automated testing frameworks 12
- 14. Entities Not same asentity beans 13
- 15. Entity Characteristics - Persistability • Entities must be persistable • State can be represented in a data store • Entities can be manipulated without having persistent repercussions – app must use API 14
- 16. Entity Characteristics -Identity • Key that uniquely identifies an instance • Persistent identity • Equivalent to primary key 15
- 17. Entity Characteristics - Transactionality • Adds, updates and deletes normally occur in a transaction • Changes succeed or fail atomically • In memory entities 16
- 18. Entity Characteristics -Granularity • Not primitives, wrappers, built-in objects • Are business domain objects that mean something • Should be fairly lightweight objects 17
- 19. Entity Manager • Interfaceencapsulating most persistence functionality • Set of managed instances is named persistence context 18
- 20. Queries • Use JPQLsyntax • Can be defined statically (named) or dynamically • Dynamic queries supply query criteria 19
- 21. JPA’s future -Independence • Break free from the EJB specification • Will get it’s own JSR for future evolution 20
- 22. The End 5 minutesof question time starts now!
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