I paint to systematize confusion and thus to help discredit completely the world of reality.
—Salvador Dali, About The Persistence of Memory
Java objects live in computer memory and normally vanish when the program that created them terminates. The lifecycle of most objects ends then. However, some objects must survive for a longer period of time. Databases and files are common datastores that you can use to keep these objects around for extended periods of time. The application layer that deals with mapping objects from memory to datastores is called the persistence layer, and the place where these objects are stored is called the persistence tier (see the Persistence section in Chapter 5).
The simplest type of ...