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.

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