Java Persistence API. Martin Krajčí Systinet / HP. CZJUG

Transcription

1 Java Persistence API Martin Krajčí Systinet / HP

2 Content JPA introduction Entities Relationships, Inheritance, JPQL Callbacks, Listeners, Transactions EntityManager, PeristenceContext Hibernate vs. Toplink, IDE support Demo application

3 Java persistence comparision September 2006 results

4 Primary features Simple to use and intuitive to learn Configure by exception (smart defaults) POJO development model Object-oriented, inheritance, polymorphism, etc. Standardized metadata for O/R mapping (annotations, XML) Entity detachment to other tier or JVMs Java persistence query language Java SE and EE persitence model Support pluggable persistence providers

5 JPA vendors Toplink Essential (Oracle; CDDL) Hibernate (JBoss; LGPL) OpenJPA (Solarmetric/BEA; Apache 2.0) Castor (Codehaus; Apache 2.0) JPOX (JPOX; Apache 2.0) Toplink (Oracle; commercial) Kodo (BEA; commercial) CocoBase (Thoughtinc; commercial) SAP JPA (SAP; commercial)

6 Content JPA introduction Entities Relationships, Inheritance, JPQL Callbacks, Listeners, Transactions EntityManager, PeristenceContext Hibernate vs. Toplink, IDE support Demo application

7 Entities Serializable POJO annotated Persistent state Defined by persistent fields or properties Entities may also have transient transient Optimistic locking Can be a concrete or abstract class

8 Entity identification Persistent identity must @IdClass Primary key generation TABLE, SEQUENCE, IDENTITY, AUTO

9 Cascade & Fetch type CascadeType ALL, PERSIST, MERGE, REMOVE, REFRESH FetchType LAZY, EAGER

10 Entity lifecycle

11 Update and Detach Updates are flushed Before query is executed Transaction commit Explicit flush using EM.flush() Detach Persistent context ends EM.clear() is called deserialized

12 Content JPA introduction Entities Relationships, Inheritance, JPQL Callbacks, Listeners, Transactions EntityManager, PeristenceContext Hibernate vs. Toplink, IDE support Demo application

13 Relationships Supports composition and Relationships (uni/bi directional) One-to-one, one-to-many, many-to-one, many-tomany Bidirectional relationships have owning and inverse for FK definition

14 Inheritance Mixed inheritance hierarchies, entities and non-entities, either concrete or Doesn't map to any table, can not SINGLE_TABLE, JOINED, TABLE_PER_CLASS

15 Inheritance

16 JPQL JPA supports static (named), dynamic and native precompiled, createnamedquery() createnativequery() Projection into non-existing classes Aggregate functions, Subquery, Inner and outer joins Paging, Max result returned, Bind parameter, Flush mode

17 Content JPA introduction Entities Relationships, Inheritance, JPQL Callbacks, Listeners, Transactions EntityManager, PeristenceContext Hibernate vs. Toplink, IDE support Demo application

18 Callback & Listeners Attached to - when application calls after the SQL when application calls after the SQL when a container detects that the instance is after the SQL after the instance was loaded Listener methods are defined on nonentity classes

19 Transactions In SE transactions and bootstraping must be handled by the application code EntityTransaction begin(), commit(), setrollbackonly(), rollback(), isactive() EE transactions are always REQUIRED, REQUIRES_NEW, SUPPORTS NOT_SUPPORTED, NEVER, MANDATORY

20 Content JPA introduction Entities Relationships, Inheritance, JPQL Callbacks, Listeners, Transactions EntityManager, PeristenceContext Hibernate vs. Toplink, IDE support Demo application

21 Packaging persistence.xml Defines Name of persistence unit Transaction strategy for EM Etities Persistence provider O/R mapping file (overrides annotations) Persistent Unit Set of entities that are mapped to the single DB and their mapping metadata

22 Entity Manager & Persistence context Two types of EntityManagers Container managed Application managed in SE/EE EntityManager, EntityManagerFactory Two types of Persistence context Transaction-scoped PersistenceContextType.TRANSACTION Extended (new to java ORM) PersistenceContextType.EXTENDED

23 Content JPA introduction Entities Relationships, Inheritance, JPQL Callbacks, Listeners, Transactions EntityManager, PeristenceContext Hibernate vs. Toplink, IDE support Demo application

24 Hibernate vs. Toplink Essential 13 files, 4.2 MB Cleaner DDL generation 2 files, 2.5 MB Better documentation Checks integrity Finer logging support Showsql more verbose

25 JPA IDE support Eclipse Dali plugin Netbeans 5.5

26 Content JPA introduction Entities Relationships, Inheritance, JPQL Callbacks, Listeners, Transactions EntityManager, PeristenceContext Hibernate vs. Toplink, IDE support Demo application

27 Demo application - UML

28 Demo application - Layers

29 JPA usage JPA + Spring using JpaDaoSupport JPA + Spring in SE JPA in SE JPA in EE Run on Toplink Essential, Hibernate, JBoss

30 References Nice Documentations JPA Extensions JPA IDE comparision Java persistence comparision

31 Questions & Answers Now OR Thanx for attention