21.10. Querying for revisions, at which entities of a given class changed

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The entry point for this type of queries is:

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<pre class="prettyprint highlight">`AuditQuery query = getAuditReader().createQuery()
    .forRevisionsOfEntity( MyEntity.class, false, true );`</pre>
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You can add constraints to this query in the same way as to the previous one.
There are some additional possibilities:

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1. using AuditEntity.revisionNumber() you can specify constraints, projections and order on the revision number, in which the audited entity was modified
2. similarly, using AuditEntity.revisionProperty( propertyName ) you can specify constraints, projections and order on a property of the revision entity, corresponding to the revision in which the audited entity was modified

3. AuditEntity.revisionType() gives you access as above to the type of the revision (ADD, MOD, DEL). </div>

   Using these methods, you can order the query results by revision number, set projection or constraint the revision number to be greater or less than a specified value, etc. For example, the following query will select the smallest revision number, at which entity of class MyEntity with id entityId has changed, after revision number 42:

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   `Number revision = (Number) getAuditReader().createQuery()

   .forRevisionsOfEntity( MyEntity.class, false, true )
   .setProjection( AuditEntity.revisionNumber().min() )
   .add( AuditEntity.id().eq( entityId ) )
   .add( AuditEntity.revisionNumber().gt( 42 ) )
   .getSingleResult();`</pre>
   

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   The second additional feature you can use in queries for revisions is the ability to maximize/minimize a property. For example, if you want to select the smallest possibler revision at which the value of the actualDate for a given entity was larger then a given value:

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   `Number revision = (Number) getAuditReader().createQuery()

   .forRevisionsOfEntity( MyEntity.class, false, true) // We are only interested in the first revision
   .setProjection( AuditEntity.revisionNumber().min() )
   .add( AuditEntity.property( "actualDate" ).minimize()
   .add( AuditEntity.property( "actualDate" ).ge( givenDate ) )
   .add( AuditEntity.id().eq( givenEntityId ) )) .getSingleResult();`</pre>
   

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   The minimize() and maximize() methods return a criteria, to which you can add constraints, which must be met by the entities with the maximized/minimized properties.

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   AggregatedAuditExpression#computeAggregationInInstanceContext() enables the possibility to compute aggregated expression in the context of each entity instance separately. It turns out useful when querying for latest revisions of all entities of a particular type.

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   You probably also noticed that there are two boolean parameters, passed when creating the query.

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   `selectEntitiesOnly`

   the first parameter is only valid when you don’t set an explicit projection. If true, the result of the query will be a list of entities (which changed at revisions satisfying the specified constraints). If false, the result will be a list of three element arrays:

4. the first element will be the changed entity instance.

5. the second will be an entity containing revision data (if no custom entity is used, this will be an instance of DefaultRevisionEntity).

6. the third will be the type of the revision (one of the values of the RevisionType enumeration: ADD, MOD, DEL). </div> </dd>

   `selectDeletedEntities`

   the second parameter specifies if revisions, in which the entity was deleted should be included in the results. If yes, such entities will have the revision type DEL and all fields, except the id, null.

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