- This primary key generation algorithm is able to generate primary key value on the basis of the sequence provided by the underlying Database.
- This algorithm is able to generate primary key values of the data types like short, int, long, etc.
- This algorithm required “sequence” input parameter with the sequence name as value in order to generate primary key value.
- If we have not provided any sequence name as input parameter then this algorithm is able to take “hibernate_sequence” as default sequence name, here developers must create “hibernate_sequence” in database explicitly.
- This algorithm is supported by almost all the databases which are supporting sequences like Oracle, DB2, etc.
- This algorithm is represented by Hibernate Software in the form of a short name like “sequence” and in the form of a predefined class like “org.hibernate.id.SequenceGenerator”.
SQL>create sequence my_sequence increment by 5; SQL>commit;
<?xml version = "1.0" encoding = "utf-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <hibernate-mapping> <class name="com.ashok.hibernate.sample.model.Employee" table="emp"> <id name="id" type="int" column="id"> <generator class="sequence"> <param name="sequence">my_sequence</param> </generator> </id> <property name="empName" column="emp_name" type="string" /> <property name="address" column="address" type="string" /> <property name="salary" column="salary" type="float" /> </class> </hibernate-mapping>
If we don’t want to use explicit sequence then we must create default sequence in database, that is, “hibernate_sequence”.
SQL>create sequence hibernate_sequence increment by 5;