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ORM, JPA, & Hibernate Overview
Brett Meyer gave an overview of Hibernate ORM and JPA. He discussed that ORM maps Java objects to relational databases for persistence beyond the life of a program. JPA is the Java standard for ORM that provides portability, while Hibernate is a full-featured JPA implementation with additional native features. Hibernate allows focusing on business logic rather than data access details and provides performance, concurrency, and extensibility benefits over traditional JDBC usage.
ORM, JPA, & Hibernate Overview
- 1. Hibernate ORM & JPAOverview Brett Meyer Senior Software Engineer Hibernate ORM, Red Hat
- 2. Brett Meyer • JBossOverlord (SOA Governance) • Hibernate ORM – ORM 4 & 5 development – Hibernate OSGi – Developer community engagement – Red Hat support, Hibernate engineering lead • Other contributions – Apache Camel – Infinispan • Contact me – @brettemeyer or +brettmeyer – Freenode IRC: brmeyer
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- 4. ORM? JPA? • ORM:Object/Relational Mapping • JPA: Java Persistence API • Hibernate ORM provides its own native API, in addition to full JPA support • Annotations and XML
- 5. Overview • JDBC • WhyORM? • Why JPA? • Hibernate ORM • Demos
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- 7. JDBC • “Java DatabaseConnectivity” • Java SE library for querying/updating database data • Mainly focused on relational DBs • Manages Connections to the DB, either directly or through a 3rd party “Connection Pool” • Database vendors provide their own JDBC driver libraries
- 8. JDBC (cont'd) • APIabstracts common interactions, data types, etc. • Execute SQL through “Statements” • Query returns received through “ResultSets” • Transactional • Cacheable
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- 11. ORM • “Object/Relational Mapping” •“Persistence”: Data objects outlive the JVM app • Maps Java POJOs to relational databases (one type of “persistence”)
- 12. Why ORM? • “DomainModel” pattern – Focus on business concepts, not relational DB structure – Interconnected objects – Each object is a meaningful individual/concept – OO concepts: inheritance, object identity, etc. – Navigate data by walking the object graph, not the explicit relational model
- 13. Why ORM? (cont'd) •Increased development speed & reduced code – No “by-hand” mapping of JDBC ResultSets to POJOs – Less work synchronizing code with relational DB changes – Less JBDC boilerplate (repetitious CRUD) – Focus on business logic
- 14. Why ORM? (cont'd) •Portability – Mostly DB independent (exception: some types of features, identifier generation, etc.) – Query abstractions (OO APIs, OO- structured languages, etc.) – Vendor-specific SQL is auto generated
- 15. Why ORM? (cont'd) •Performance – Granular control of “when”, “how”, “how much” data/relationships to load, based on the business logic – Object and query caching • Concurrency & multiple-tenancy • Transactional • Scalable • Extendable (many types of extension points)
- 16. ORM FUD • “ORMsare slow and generally awful.” – http://www.slideshare.net/brmeyer/hibernate-orm • “ORMs are over complicated.” – Back in the EJB/XML days, maybe. – Annotations FTW!
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- 19. JPA • “Java PersistenceAPI” • JSR 317 (2.0) & JSR 338 (2.1) • Included in both Java SE & Java EE • Provides portability between JPA implementations (with caveats) • Same ORM concepts, but standardized API and query language (JPQL)
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- 22. Hibernate ORM • JPAimplementation and 100% TCK compliant • “Native” features – HQL (Hibernate Query Language): similar to JPQL, but extended – Criteria API – Performance: Fetch strategies, caching, bytecode enhancement, etc. – Extension points – Rich tool set (schema generation/validation, etc.) • Part of JBoss Community
- 23. Hibernate Family • Notjust ORM • Hibernate Spatial • Hibernate Envers • Hibernate OSGi • Hibernate Search • Hibernate OGM • Hibernate Validator • Hibernate Shards • http://www.slideshare.net/brmeyer/hibernate-orm-features
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- 26. QUESTIONS? • Q&A • FreenodeIRC: brmeyer • @brettemeyer • +brettmeyer