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

3. github.com/brmeyer
/HibernateDemos
slideshare.net/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

24. We've barely
scratched the
surface!

25. How to Help:
hibernate.org
/orm/contribute

26. QUESTIONS?
• Q&A
• Freenode IRC: brmeyer
• @brettemeyer
• +brettmeyer