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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.
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ORM, JPA, & Hibernate Overview
- 1.Hibernate ORM& JPAOverviewBrett MeyerSenior Software EngineerHibernate 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 nativeAPI, 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 databasedata• Mainly focused on relational DBs• Manages Connections to the DB, either directlyor through a 3rdparty “Connection Pool”• Database vendors provide their own JDBCdriver 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 theJVM app• Maps Java POJOs to relationaldatabases (one type of “persistence”)
- 12.Why ORM?• “DomainModel” pattern– Focus on business concepts, not relational DBstructure– Interconnected objects– Each object is a meaningful individual/concept– OO concepts: inheritance, object identity, etc.– Navigate data by walking the object graph, not theexplicit relational model
- 13.Why ORM? (cont'd)•Increased development speed &reduced code– No “by-hand” mapping of JDBC ResultSetsto POJOs– Less work synchronizing code withrelational DB changes– Less JBDC boilerplate (repetitious CRUD)– Focus on business logic
- 14.Why ORM? (cont'd)•Portability– Mostly DB independent (exception: sometypes 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 JPAimplementations (with caveats)• Same ORM concepts, but standardizedAPI 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, butextended– Criteria API– Performance: Fetch strategies, caching, bytecodeenhancement, 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