You are viewing an old version of this page. View the current version.

Compare with Current View Page History

« Previous Version 3 Next »

On this Page:
Each class of which instances have to be persistent must have the stereotype <<PersistentState>>. One or more attributes of this class must have the stereotype <<PrimaryKey>>, uniquely identifying an object. A persistent state class optionally has attributes stereotyped <<SearchKey>>.

Primary Key and Search Key Attributes

While primary keys are used to identify and address a specific unique object, search keys are used to query for a list of objects. If you want to query for a list using primary key fields, these fields also require setting the <<SearchKey>> stereotype.
Only attributes of primitive types can be marked as primary or search key.

Search keys that have not been initialized are NULL. Keep this in mind, if you want to look-up all persistent state objects using mySearchKey like '%'.  Either, you need to initialize the search key, or you need to extend the search phrase to mySearchKey like '%' or mySearchKey is NULL.

Figure: A Persistent State Class

Attributes having stereotype PrimaryKey or SearchKey are represented with different icons in the containment tree of MagicDraw (see picture below).

Figure: Stereotyped Attributes of a Persistent State Class

Persistent Data

Attributes that are not marked as primary key or search key contain persistent data.

Builder 7.5.0 You can mark such attributes as private by applying stereotype <<E2EPrivate>>, but we do not recommend this.

Attributes marked as private are not being serialized by the xUML Runtime. As the Runtime cannot distinct the context of <<E2EPrivate>>, this results in such attributes not being saved between transitions and states.

Refer to Hiding Attributes From Interfaces for more information.

Modifying Persistent State Classes

Be careful with modifying persistent state classes of a service already running on a Bridge. If you deploy the modified service, the service might refuse to start-up and throw an error:

Info: Loaded addon PState_AddOn successfully.
Fatal: Found persistent state objects of class "<name of the old class>" that does not exist in the repository anymore.
Fatal: Detected objects for which no metadata exist in the repository. Correct the problem either by restoring class definitions in the model or by deleting corresponding objects.
Fatal: Initializing service "PersistentStateService" failed

This can happen e.g. if you remove or change the name of the persistent state class but the persistent state database still contains objects of the old class. These objects become orphaned in this case.
You can fix this in two ways:

  • Delete all old persistent state objects using the Bridge (see Deleting Persistent State Objects).
  • Redeploy the old service and let it work all persistent state objects before deploying the new one.
  • No labels