If there is an existing data layer (e.g. DAO) that needs to be converted to Cayenne, currently most of the mapping tasks will have to be done manually using the Modeler.
|Note for EOF Users|
CayenneModeler provides import function for the EOModels. So most of the mapping conversions should be automatic.
In any case there is a good chance of reusing business methods already defined in a persistence framework. And definitely any existing database can be used as is. One possible approach to conversion is to follow these steps:
- Reverse engineer the database schema into a new Cayenne mapping project.
- Update class names and packages match the names of the existing classes.
- Run class generation using "generation gap" pattern (to create subclass/superclass pair for each entity). This would only create superclasses with set/get methods for persistent properties, without touching the existing classes.
- Modify existing DAO classes to change the superclass to a corresponding generated one (e.g. "Employee extends _Employee").
- Remove any persistent properties with their setters and getters from the subclass.
- Remove all the DAO-specific persistence code.
- Rewrite any other "business" methods to use DataContext for data operations.
See the following topics explaining individual tasks involved: