13.7. Envers

Procedure 13.6. Define a Auditing Strategy

• Configure the org.hibernate.envers.audit_strategy property in the persistence.xml file of the application. If the property is not set in the persistence.xml file, then the default audit strategy is used.

  Example 13.28. Set the Default Audit Strategy

  <property name="org.hibernate.envers.audit_strategy" value="org.hibernate.envers.strategy.DefaultAuditStrategy"/>
  

  Example 13.29. Set the Validity Audit Strategy

  <property name="org.hibernate.envers.audit_strategy" value="org.hibernate.envers.strategy.ValidityAuditStrategy"/>
  

Procedure 13.7. Add Auditing Support to a JPA Entity

1. Configure the available auditing parameters to suit the deployment: Section 13.7.5.1, “Configure Envers Parameters”.
2. Open the JPA entity to be audited.
3. Import the org.hibernate.envers.Audited interface.
4. Apply the @Audited annotation to each field or property to be audited, or apply it once to the whole class.

   Example 13.30. Audit Two Fields

   import org.hibernate.envers.Audited;
   
   import javax.persistence.Entity;
   import javax.persistence.Id;
   import javax.persistence.GeneratedValue;
   import javax.persistence.Column;
   
   @Entity
   public class Person {
       @Id
       @GeneratedValue
       private int id;
   
       @Audited
       private String name;
   
       private String surname;
   
       @ManyToOne
       @Audited
       private Address address;
   
       // add getters, setters, constructors, equals and hashCode here
   }
   

   Example 13.31. Audit an entire Class

   import org.hibernate.envers.Audited;
   
   import javax.persistence.Entity;
   import javax.persistence.Id;
   import javax.persistence.GeneratedValue;
   import javax.persistence.Column;
   
   @Entity
   @Audited
   public class Person {
       @Id
       @GeneratedValue
       private int id;
   
       private String name;
   
       private String surname;
   
       @ManyToOne
       private Address address;
   
       // add getters, setters, constructors, equals and hashCode here
   }
   

Procedure 13.8. Configure Envers Parameters

1. Open the persistence.xml file for the application.
2. Add, remove or configure Envers properties as required. For a list of available properties, refer to Section 13.7.5.4, “Envers Configuration Properties”.

Procedure 13.9. Enable/Disable Auditing

1. Subclass the AuditEventListener class.
2. Override the following methods that are called on Hibernate events:
   • onPostInsert
   • onPostUpdate
   • onPostDelete
   • onPreUpdateCollection
   • onPreRemoveCollection
   • onPostRecreateCollection
3. Specify the subclass as the listener for the events.
4. Determine if the change should be audited.
5. Pass the call to the superclass if the change should be audited.

Procedure 13.10. Implement Conditional Auditing

1. Set the hibernate.listeners.envers.autoRegister Hibernate property to false in the persistence.xml file.
2. Subclass each event listener to be overridden. Place the conditional auditing logic in the subclass, and call the super method if auditing should be performed.
3. Create a custom implementation of org.hibernate.integrator.spi.Integrator, similar to org.hibernate.envers.event.EnversIntegrator. Use the event listener subclasses created in step two, rather than the default classes.
4. Add a META-INF/services/org.hibernate.integrator.spi.Integrator file to the jar. This file should contain the fully qualified name of the class implementing the interface.