So we have now defined which classes/fields are to be persisted and indeed how they match to the datastore schema. We now need to define the actual persistence of our objects and how we retrieve them from persistence. This is termed the persistence code. The persistence code can be split into several sections.

• Enhancing your persistable classes
• Generating the tables for the database schema when you are using a new schema
• Creating a PersistenceManagerFactory to connect to a datastore
• Creating a PersistenceManager to provide the interface to persisting/accessing objects
• Controlling transactions
• Accessing persisted object via queries, using JDOQL, or SQL
• Refining the persistence process to improve performance, maybe using caching
• Logging of the persistence process