CHAPTER 9 Working with objects Figure 9.1 Object (Web site templates)
CHAPTER 9 Working with objects Figure 9.1 Object states and their transitions as triggered by persistence manager operations Transient objects Objects instantiated using the new operator aren t immediately persistent. Their state is transient, which means they aren t associated with any database table row and so their state is lost as soon as they re no longer referenced by any other object. These objects have a lifespan that effectively ends at that time, and they become inaccessible and available for garbage collection. Java Persistence doesn t include a term for this state; entity objects you just instantiated are new. We ll continue to refer to them as transient to emphasize the potential for these instances to become managed by a persistence service. Hibernate and Java Persistence consider all transient instances to be nontransactional; any modification of a transient instance isn t known to a persistence context. This means that Hibernate doesn t provide any roll-back functionality for transient objects. Objects that are referenced only by other transient instances are, by default, also transient. For an instance to transition from transient to persistent state, to become managed, requires either a call to the persistence manager or the creation of a reference from an already persistent instance. Persistent objects A persistent instance is an entity instance with a database identity, as defined in chapter 4, section 4.2, Mapping entities with identity. That means a persistent and
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