Hibernate - Inheritance – Strategy 2 ( with Annotation ) : Table Per Sub Class Hierarchy

Hibernate - Inheritance – Strategy 2 ( with Annotation ) : Table Per Sub Class Hierarchy 

Hibernate Annotation ( Inheritance – Strategy 2 : Table Per Sub Class Hierarchy ) Application

Inheritance Mapping  Hibernate supports 3 basic inheritance mapping strategies. 1. Table per class hierarchy  2. Table per subclass 3. Table per concrete class
For this example we use below assotations.  @Inheritance( strategy = InheritanceType.JOINED) in the parent class and @PrimaryKeyJoinColumn( name = "empId" ) annotation in the sub class

 

 

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 - Hibernate Configurations ( hibernate.cfg.xml )  Step 3 - 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 - Hibernate Configurations

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

 

 

 

Step 3 - Create Execute class

 
Create a ExecuteEmployee class to do the execution.
 

package impl;

import java.util.Iterator;

import java.util.List;

import org.hibernate.Session;

import org.hibernate.Transaction;

import org.hibernate.cfg.AnnotationConfiguration;

import pojo.ContractEmployee;

import pojo.Employee;

import pojo.PermanentEmployee;

public class ExecuteEmployee {

/**

* @param args

*/

public static void main(String[] args) {

  ExecuteEmployee executeEmployee = new ExecuteEmployee();

  executeEmployee.addEmployee();

  executeEmployee.listEmployee();

}

private void addEmployee(){

  Transaction transaction = null;

  Session hbSession = new AnnotationConfiguration().configure("config/hibernate.cfg.xml")

   .buildSessionFactory().openSession();

 

    try{

       transaction = hbSession.beginTransaction();

       Employee employee = new Employee();

       employee.setEmpId(100100);

       employee.setFirstName("Sanjeeva");

       employee.setLastName("Pathirana");

       PermanentEmployee permanentEmployee = new PermanentEmployee();

       permanentEmployee.setEmpId(100101);

       permanentEmployee.setFirstName("Sandamali");

       permanentEmployee.setLastName("Silva");

       permanentEmployee.setSalary(50000);

       permanentEmployee.setBonus(2500);

       ContractEmployee contractEmployee = new ContractEmployee();

       contractEmployee.setEmpId(100102);

       contractEmployee.setFirstName("Thinuli");

       contractEmployee.setLastName("Pathirana");

       contractEmployee.setPerhourrate(150);

       contractEmployee.setContractperiod(6);

       hbSession.save(employee);

       hbSession.save(permanentEmployee);

       hbSession.save(contractEmployee);

       hbSession.getTransaction().commit();

       System.out.println("Insert All Employees ");

    }catch (Exception e) {

       if(null != transaction){

          transaction.rollback();

       }

       e.printStackTrace();

    }finally{

          hbSession.flush();

          hbSession.close();

    }

}

private void listEmployee(){

    Transaction transaction = null;

    Session hbSession = new AnnotationConfiguration().configure("config/hibernate.cfg.xml")

                        .buildSessionFactory().openSession();

 

    try{

        transaction = hbSession.beginTransaction();

 

        @SuppressWarnings("unchecked")

        List<Employee> employeesList = hbSession.createQuery("FROM Employee").list();

 

        for(Iterator<Employee> iterator = employeesList.iterator(); iterator.hasNext();){

            Employee employee = iterator.next();

            System.out.println("");

            System.out.println("EmpId : " + employee.getEmpId());

            System.out.println("FirstName : " + employee.getFirstName());

            System.out.println("LastName : " + employee.getLastName());

            if(employee instanceof PermanentEmployee ){

               System.out.println("Salary : " + ((PermanentEmployee)employee).getSalary() );

               System.out.println("Bonus : " + ((PermanentEmployee)employee).getBonus() );

            }else{

               System.out.println("Salary : - " );

               System.out.println("Bonus : - ");

            }

            if(employee instanceof ContractEmployee ){

               System.out.println("Perhourrate : " +    ((ContractEmployee)employee).getPerhourrate());

               System.out.println("Contract Period : " + ((ContractEmployee)employee).getContractperiod() );

            }else{

               System.out.println("Perhourrate : - ");

               System.out.println("Contract Period : - ");

            }

         }

         hbSession.getTransaction().commit();

    

     }catch (Exception e) {

         if(null != transaction){

            transaction.rollback();

         }

         e.printStackTrace();

     }finally{

         hbSession.flush();

         hbSession.close();

     }

   }

}

Out put on the above application as follows.