HIbernate - Inheritance – Strategy 3 : Table Per Concrete Class Hierarchy

HIbernate - Inheritance – Strategy 3 : Table Per Concrete Class Hierarchy

Hibernate Application ( Inheritance – Strategy 3 : Table Per Class Hierarchy ) 

 

Inheritance Mapping

Hibernate supports 3 basic inheritance mapping strategies. 1. Table per class hierarchy  2. Table per subclass  3. Table per concrete class  As per the below example there will be 3 tables and no relations to each other.

There is no null values in the table since tables are created per class. Disadvantage of this approach is, it created duplicate columns. To do the table map, use union-subclass element.

 

 

Suppose you have the base Employee class, with PermanentEmployee and ContractEmployee as subclasses. 
Steps - 
Step 1 - Create POJO classes ( Employee.java and PermanentEmployee, ContractEmployee sub-classes )
Step 2 - Create mapping file ( employee.hbm.xml )
Step 3 - Hibernate Configurations ( hibernate.cfg.xml ) 
Step 4 - Create class to do the execution ( ExecuteEmployee.java ) 

Step 1 - Create POJO classes 

 
Create POJO (Plain Old Java Object) classes that represents the Employee, PermanentEmployee and ContractEmployee.

 

 

 

 

 

 

 

Step 2 - Create mapping file 
Create a mapping file “employee.hbm.xml” which maps, “employee”, “permanentemployee”, “contractemployee” tables in the database by using <union-subclass tag. 

<union-subclass name="pojo.PermanentEmployee" table="permanentemployee">

..

</union-subclass>

 

 

 

Step 3 - Hibernate Configurations

 

Create configuration file name as hibernate.cfg.xml and save it.

 

 

 

Step 4 - Create Execute class

 

Create a ExecuteEmployee class to do the execution.

 

 

 

 

 

 

Out put on the above application as follows.