Each PersistenceManager is responsible for managing the JDO identities of the persistent objects in its cache. The following methods allow you to interact with the management of JDO identities:
getObjectIdClass: Returns the JDO identity class used for the given persistence-capable class.
newObjectIdInstance: This method is used to re-create JDO identity objects from the string returned by their toString method. Given a persistence-capable class and a JDO identity string, the method constructs a JDO identity object. Using the getObjectById method described below, this identity object can then be employed to obtain the persistent instance whose identity was used to create the string in the first place.
getObjectId: Returns the JDO identity object for a persistent instance managed by this PersistenceManager.
getObjectById: This method returns the persistent instance corresponding to the given JDO identity object. If the instance is already cached, the cached version will be returned. Otherwise, a new instance will be constructed, and may or may not be loaded with data from the data store (some implementations might return a hollow instance).
If the validate parameter of this method is set to true, then the JDO implementation will throw an exception if the data store record for the given JDO identity does not exist. Otherwise, some implementations might return a hollow instance for the missing record, and an exception will not be thrown until you attempt to access one of its persistent fields.