21.1. Basics

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To audit changes that are performed on an entity, you only need two things:

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• the hibernate-envers jar on the classpath,

• an @Audited annotation on the entity. </div>

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  Unlike in previous versions, you no longer need to specify listeners in the Hibernate configuration file. Just putting the Envers jar on the classpath is enough because listeners will be registered automatically.

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  And that’s all. You can create, modify and delete the entities as always.

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  If you look at the generated schema for your entities, or at the data persisted by Hibernate, you will notice that there are no changes. However, for each audited entity, a new table is introduced - entity_table_AUD, which stores the historical data, whenever you commit a transaction.

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  Envers automatically creates audit tables if hibernate.hbm2ddl.auto option is set to create, create-drop or update. Otherwise, to export complete database schema programmatically, use org.hibernate.envers.tools.hbm2ddl.EnversSchemaGenerator. Appropriate DDL statements can be also generated with Ant task described later in this manual.

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  Instead of annotating the whole class and auditing all properties, you can annotate only some persistent properties with @Audited. This will cause only these properties to be audited.

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  The audit (history) of an entity can be accessed using the AuditReader interface, which can be obtained having an open EntityManager or Session via the AuditReaderFactory. See the Javadocs) for these classes for details on the functionality offered.

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