The entire OMERO application (on a single JVM) resides in a single ome.system.OmeroContext. Each call belongs additionally to a single org.hibernate.Session (which can span over multiple calls) and to a single ome.model.meta.Event (which is restricted to a single task).

OmeroContext

The container for all Omero applications is the OmeroContext (source file). Based on the Spring configuration backing the context, it can be one of : client, internal, or managed. The use of a ServiceFactory(code) simplifies this usage for the client. See OmeroClientLibrary for more information.

Hibernate Sessions

A Hibernate Session comprises a Unit-of-Work which translates for OMERO's ObjectModel to a relational database. It keeps references to all DB-backed objects so that within a single session object-identity stays constant and objects changes can be persisted.

A session can span multiple calls by being disconnected from the underlying database transaction and, then, reconnected to a new transaction on the next call (See SessionHandler for the implementation).

! Event

For more information about Events see OmeroEvents.