Identifier mappings in Hibernate 3
Identifier mappings - The unsaved-value attribute is now optional, in most cases. Hibernate will use unsaved-value="0" as the default, where that is sensible. Note: In Hibernate3, it is no longer necessary to implement Interceptor.isUnsaved() when using natural keys (assigned identifiers or composite identifiers) and detached objects. In the absence of any "hints", Hibernate will query the database to determine if an object is new or detached. However, the use of Interceptor.isUnsaved() might result in higher performance, since the database query can be avoided.