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ORM, JPA, & Hibernate Overview
- 1. Hibernate ORM & JPA Overview Brett Meyer Senior Software Engineer Hibernate ORM, Red Hat
- 2. Brett Meyer • JBoss Overlord (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
- 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 • Why ORM? • Why JPA? • Hibernate ORM • Demos
- 6. JDBC
- 7. JDBC • “Java Database Connectivity” • 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) • API abstracts common interactions, data types, etc. • Execute SQL through “Statements” • Query returns received through “ResultSets” • Transactional • Cacheable
- 9. JDBC Demo
- 10. Why ORM?
- 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? • “Domain Model” 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 • “ORMs are slow and generally awful.” – http://www.slideshare.net/brmeyer/hibernate-orm • “ORMs are over complicated.” – Back in the EJB/XML days, maybe. – Annotations FTW!
- 17. ORM Demo
- 18. Why JPA?
- 19. JPA • “Java Persistence API” • 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)
- 20. JPA Demo
- 21. Hibernate ORM
- 22. Hibernate ORM • JPA implementation 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 • Not just ORM • Hibernate Spatial • Hibernate Envers • Hibernate OSGi • Hibernate Search • Hibernate OGM • Hibernate Validator • Hibernate Shards • http://www.slideshare.net/brmeyer/hibernate-orm-features
- 26. QUESTIONS? • Q&A • Freenode IRC: brmeyer • @brettemeyer • +brettmeyer