Java Data Objects

State Interrogation

The JDOHelper class provides the following methods to interrogate the state of an instance:

static boolean isPersistent(Object obj);
static boolean isTransactional(Object obj);
static boolean isDirty(Object obj);
static boolean isNew(Object obj);
static boolean isDeleted(Object obj);

Each of these methods returns false if the instance is null, transient, or of a class that is not persistent. Otherwise, these methods return the following:

isPersistent( )

Returns true for an instance that represents a persistent object in the datastore

isTransactional( )

Returns true for an instance whose state is associated with the current transaction

isDirty( )

Returns true for an instance whose state has changed in the current transaction

isNew( )

Returns true for an instance made persistent in the current transaction

isDeleted( )

Returns true if the instance has been deleted in the current transaction

Table 11-1 specifies the values these methods return for each required lifecycle state. You could write a method that calls each of these methods and returns a String denoting the instance’s lifecycle state. This can be useful if you are debugging or would like to know the lifecycle state of instances.

Table 11-1. State interrogation method return values

State of Instance	isPersistent( )	isTransactional( )	isDirty( )	isNew( )	isDeleted( )
Transient	false	false	false	false	false
Hollow	true	false	false	false	false
Persistent-new	true	true	true	true	false
Persistent-clean	true	true	false	false	false
Persistent-dirty ...