Datastore Control

Sometimes a datastore has particular requirements, and maybe is out of direct control of an application being managed by a different group. In this situation you may have to configure the datastore layer to meet these requirements.



Read-Only

If your datastore is read-only (you can't add/update/delete any data in it), obviously you could just configure your application to not perform these operations. An alternative is to set the EntityManagerFactory as "read-only". You do this by setting the persistence property datanucleus.readOnlyDatastore to true .

From now on, whenever you perform a persistence operation that implies a change in datastore data, the JPA operation will throw an exception. You can change this behaviour using the persistence property datanucleus.readOnlyDatastoreAction with values of "EXCEPTION" (default), and "IGNORE". "IGNORE" has the effect of simply ignoring all attempted updates to readonly objects.



Fixed Schema

Some datastores have a "schema" defining the structure of data stored within that datastore. In this case we don't want to allow updates to the structure at all. You can set this when creating your EntityManagerFactory by setting the persistence property datanucleus.fixedDatastore to true .