When we are using the hibernate the we also know about that in the mapping class must
declare the primary key column of the database table. In the Most classes always having the
JavaBeans-style property holding the unique identifier of an instance.
Id generator is used to auto generate id of objects.Different database support different types of generator. most commonly used generator that are supported by oracle are:
Increment generator uses highest value of primary key increases to generator id value.
<id name="propertyName" type="typename" column="column_name" unsaved-value="null|any|none|undefined|id_value" access="field|property|ClassName"> node="element-name|@attribute-name|element/@attribute|." <generator class="generatorClass"/> </id>
If the name attribute is missing, that assumed that the class has no identifier property.
and the unsaved-value attribute is almost never needed in hibernate3.
There is an altern