Hibernate is an ambitious project that aims to provide a complete solution to the problem of managing persistent data in Java. Today, Hibernate is not only an ORM service, but also a collection of data management tools extending well beyond ORM.
■ Hibernate ORM — Hibernate ORM consists of a core, a base service for persistence with SQL databases, and a native proprietary API. Hibernate ORM is the foundation for several of the other projects and is the oldest Hibernate project. You can use Hibernate ORM on its own, independent of any framework or any particular runtime environment with all JDKs. It works in every Java EE/J2EE application server, in Swing applications, in a simple servlet container, and so on. As long as you can configure a data source for Hibernate, it works.
■ Hibernate EntityManager — This is Hibernate’s implementation of the standard Java Persistence APIs, an optional module you can stack on top of Hibernate ORM. You can fall back to Hibernate when a plain Hibernate interface or even a JDBC Connection is needed. Hibernate’s native features are a superset of the JPA persistence features in every respect.
■ Hibernate Validator — Hibernate provides the reference implementation of the Bean Validation (JSR 303) specification. Independent of other Hibernate projects, it provides declarative validation for your domain model (or any other) classes.
■ Hibernate Envers — Envers is dedicated to audit logging and keeping multiple versions of data in your SQL database. This helps you add data history and audit trails to your application, similar to version control systems you might already be familiar with such as Subversion and Git.
■ Hibernate Search — Hibernate Search keeps an index of your domain model data up to date in an Apache Lucene database. It lets you query this database with a powerful and naturally integrated API. Many projects use Hibernate Search in addition to Hibernate ORM, adding full-text search capabilities. If you have a free text search form in your application’s user interface, and you want happy users, work with Hibernate Search. Hibernate Search isn’t covered in this book; you can find more information in Hibernate Search in Action by Emmanuel Bernard (Bernard, 2008).
■ Hibernate OGM — The most recent Hibernate project is the object/grid mapper. It provides JPA support for NoSQL solutions, reusing the Hibernate core engine but persisting mapped entities into a key/value-, document-, or graph-oriented data store. Hibernate OGM isn’t covered in this book.
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