21.6. Tracking entity names modified during revisions

<div class="paragraph">

By default entity types that have been changed in each revision are not being tracked.
This implies the necessity to query all tables storing audited data in order to retrieve changes made during specified revision.
Envers provides a simple mechanism that creates `REVCHANGES` table which stores entity names of modified persistent objects.
Single record encapsulates the revision identifier (foreign key to `REVINFO` table) and a string value.

</div>
<div class="paragraph">

Tracking of modified entity names can be enabled in three different ways:

</div>
<div class="olist arabic">

Set org.hibernate.envers.track_entities_changed_in_revision parameter to true. In this case org.hibernate.envers.DefaultTrackingModifiedEntitiesRevisionEntity will be implicitly used as the revision log entity.

Create a custom revision entity that extends org.hibernate.envers.DefaultTrackingModifiedEntitiesRevisionEntity class.

`@RevisionEntity
public class ExtendedRevisionEntity extends DefaultTrackingModifiedEntitiesRevisionEntity {
    ...
}`

Mark an appropriate field of a custom revision entity with @org.hibernate.envers.ModifiedEntityNames annotation. The property is required to be of Set<String> type.
```
`@RevisionEntity
public class AnnotatedTrackingRevisionEntity {
```
```
...
@ElementCollection
@JoinTable( name = "REVCHANGES", joinColumns = @JoinColumn( name = "REV" ) )
@Column( name = "ENTITYNAME" )
@ModifiedEntityNames
private Set&lt;String&gt; modifiedEntityNames;
...
```
}`</pre> </div> </div>
Users, that have chosen one of the approaches listed above, can retrieve all entities modified in a specified revision by utilizing API described in [Querying for entities modified in a given revision](#envers-tracking-modified-entities-queries).
</div>
Users are also allowed to implement custom mechanism of tracking modified entity types. In this case, they shall pass their own implementation of org.hibernate.envers.EntityTrackingRevisionListener interface as the value of @org.hibernate.envers.RevisionEntity annotation. EntityTrackingRevisionListener interface exposes one method that notifies whenever audited entity instance has been added, modified or removed within current revision boundaries.

</div>
Example 498. CustomEntityTrackingRevisionListener.java
`public class CustomEntityTrackingRevisionListener implements EntityTrackingRevisionListener {
```
@Override
public void entityChanged( Class entityClass, String entityName,
                           Serializable entityId, RevisionType revisionType,
                           Object revisionEntity ) {
    String type = entityClass.getName();
    ( ( CustomTrackingRevisionEntity ) revisionEntity ).addModifiedEntityType( type );
}

@Override
public void newRevision( Object revisionEntity ) {
}
```
}</pre> </div> </div> </div> </div> <div class="exampleblock"> <div class="title">Example 499. CustomTrackingRevisionEntity.java</div> <div class="content"> <div class="listingblock"> <div class="content"> <pre class="prettyprint highlight">@Entity @RevisionEntity( CustomEntityTrackingRevisionListener.class ) public class CustomTrackingRevisionEntity {
```
@Id
@GeneratedValue
@RevisionNumber
private int customId;

@RevisionTimestamp
private long customTimestamp;

@OneToMany( mappedBy="revision", cascade={ CascadeType.PERSIST, CascadeType.REMOVE } )
private Set&lt;ModifiedEntityTypeEntity&gt; modifiedEntityTypes = new HashSet&lt;ModifiedEntityTypeEntity&gt;();

public void addModifiedEntityType( String entityClassName ) {
    modifiedEntityTypes.add( new ModifiedEntityTypeEntity( this, entityClassName ) );
}

...
```
}</pre> </div> </div> </div> </div> <div class="exampleblock"> <div class="title">Example 500. ModifiedEntityTypeEntity.java</div> <div class="content"> <div class="listingblock"> <div class="content"> <pre class="prettyprint highlight">@Entity public class ModifiedEntityTypeEntity {
```
@Id
@GeneratedValue
private Integer id;

@ManyToOne
private CustomTrackingRevisionEntity revision;

private String entityClassName;

...
```
}</pre> </div> </div> </div> </div> <div class="listingblock"> <div class="content"> <pre class="prettyprint highlight">CustomTrackingRevisionEntity revEntity =
```
getAuditReader().findRevision( CustomTrackingRevisionEntity.class, revisionNumber );
```
Set<ModifiedEntityTypeEntity> modifiedEntityTypes = revEntity.getModifiedEntityTypes();`</pre> </div> </div> </div>

21.6. Tracking entity names modified during revisions

21.6. Tracking entity names modified during revisions

results matching ""

No results matching ""