Core Java™ Data Objects

3.13. Object Lifecycles

JDO defines a number of different states in which an in-memory persistent object can be. Principally, these states are used by the JDO implementation to determine whether the fields of an instance need to be retrieved from the datastore and, if modified, whether they need to be written back. Together, these states represent an in-memory persistent object's lifecycle with respect to JDO.

Chapter 4 describes the object lifecycle states in greater detail; however, in general, only the following basic states need to be understood:

• Transient

• Persistent

• Hollow

Figure 3-4 shows a simplified state diagram for these basic lifecycle states:

Transient denotes a normal, non-persistent Java object. When an instance of a persistence-capable ...