CDO/Hibernate Store/Auditing

Since November 2012 the CDO Hibernate Store supports auditing in the 4.2 release stream. The auditing support is based on the auditing support provided by Teneo with the notable difference that auditing and revisions are completely integrated with the CDO client side object history api.

Architecture

The CDO Hibernate Store uses the Teneo mapping engine to generate an auditing model and database schema. The auditing database schema creates audit tables for each domain type and follows the same structure as the domain model. The main differences are:

• Teneo adds audit meta data to each table (commit timestamp, validity period of an audit entry etc.)
• EReferences are not persisted as foreign keys but as strings
• Enumerates are always persisted as strings

Other than that you will see the same columns and fields in the auditing database schema.

Enabling and configuring auditing - controlling the database schema

You enable auditing by setting the following option in the server config xml file:

<property name="supportingAudits" value="true"/>

In addition all the Teneo specific options apply, see here for more information.

You can control the auditing database schema by annotating the model in the same way as for standard Teneo, with one difference auditing annotations are defined using the teneo.jpa.auditing source on the EAnnotation on the domain model. See here for more information.

Retrieving Object History - Revisions

The CDO api provides several ways of working with historical data/audit entries.

Setting a timestamp on the view/transaction

The easiest way to access to historical data is to open a view using a specific time stamp. The resources and objects retrieved through the resource (and all referenced objects) will all represent that state on that timestamp.

// open a view for a specific timestamp
CDOView audit = session.openView(commitTime3);
 
// get a resource in the state of that timestamp
CDOResource auditResource = audit.getResource(getResourcePath("/res1"));
 
// get a revision on that timestamp
Company auditCompany = (Company)auditResource.getContents().get(0);
 
// test something
assertEquals("Eclipse", auditCompany.getName());

CDOUtil.getRevisionByVersion - Comparing revisions

Another way of getting to the versions of an object is to use the

// use the auditCompany from above
final CDOObject cdoObject = CDOUtil.getCDOObject(auditCompany);
int thisVersion = cdoObject.cdoRevision().getVersion();
assertEquals(3, initialVersion);
 
final InternalCDORevision revision3 = (InternalCDORevision)CDOUtil.getRevisionByVersion(cdoObject, 3);
final InternalCDORevision revision2 = (InternalCDORevision)CDOUtil.getRevisionByVersion(cdoObject, 2);
final InternalCDORevision revision1 = (InternalCDORevision)CDOUtil.getRevisionByVersion(cdoObject, 1);
 
// note get the eclass from the revision to use the correct eclass instance
assertEquals("ESC", revision1.getValue(revision1.getEClass().getEStructuralFeature("name")));
assertEquals("Sympedia", revision2.getValue(revision1.getEClass().getEStructuralFeature("name")));
assertEquals("Eclipse", revision3.getValue(revision1.getEClass().getEStructuralFeature("name")));

You can also compare the revisions to get the details of the differences between different revisions:

CDORevisionDelta revisionDelta = revision3.compare(revision2);
for (CDOFeatureDelta featureDelta : revisionDelta.getFeatureDeltas())
{
  System.err.println(featureDelta.getFeature().getName() + " changed through changeType "
            + featureDelta.getType());
}

Note that the CDOFeatureDelta has many subclasses, checking the exact instance class and casting to it (based on the type) allows access to the change details (for example new and old value).

Limitations

• HQL queries are not executed on the audit tables but always on the domain tables, this means that HQL queries will not execute in the timestamp set on the view but always on the latest version of an object.
• Auditing entries can not be exported/imported, i.e. always the latest version of an object is exported and imported.

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