hibernate class for subclass hierarchy

Table for subclass:

In this process we map the class hierarchy to multiple tables associated with the relational foreign key.

The main advantage of this process inheritance mapping is; the relational model is completely normalized, integrity constraint definitions are maintained.

Java:

Database:

create table employee(empno int(4),ename char(16)

create table salariedemployee(empno int(4),annualSal int(4));

Ex4:

//hibernate-ineritance-join-subclass.

Employee.java

package madhav;

public class Employee {

       private int empno;

       private String ename;

       public int getEmpno() {                  

             return empno;

       }

       public void setEmpno(int empno) {

             this.empno = empno;

       }

       public String getEname() {

             return ename;

       }

       public void setEname(String ename) {

             this.ename = ename;

       }

}

SalariedEmployee.java

package madhav;

public class SalariedEmployee extends Employee{

      public double annualSal;

    public double getAnnualSal() {

          return annualSal;

    }

    public void setAnnualSal(double annualSal) {

          this.annualSal = annualSal;

    }

    public String toString()

    {

      return "salariedEmployee";

    }

}

employee.hbm.xml

<?xml version="1.0" encoding="UTF-8"?>

 <!DOCTYPE hibernate-mapping PUBLIC

"-//Hibernate/Hibernate Mapping DTD 3.0//EN"

"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

  <class name="madhav.Employee" table="employee">

   <id name="empno" type="int" column="empno" >

   <generator class="increment"/>

  </id>

  <property name="ename">

   <column name="ename" />

  </property>

 <joined-subclass name="madhav.SalariedEmployee" table="salariedemp">

 <key column="empno"></key>

 <property name="annualSal"></property>

 </joined-subclass>

 </class>

</hibernate-mapping>

hibernate.cfg.xml

<?xml version='1.0' encoding='UTF-8'?>

<!DOCTYPE hibernate-configuration PUBLIC

          "-//Hibernate/Hibernate Configuration DTD 3.0//EN"

          "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<!-- Generated by MyEclipse Hibernate Tools.                   -->

<hibernate-configuration>

    <session-factory>

        <property name="dialect">org.hibernate.dialect.MySQLDialect</property>

        <property name="connection.url">jdbc:mysql://localhost:3306/mysql</property>

        <property name="connection.username">madhav</property>

        <property name="connection.password">madhav</property>

        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>

        <property name="hbm2ddl.auto">create</property>

    <mapping resource="employee.hbm.xml"/>

    </session-factory>

</hibernate-configuration>

                                                                       

TestCase.java

package madhav;

import org.hibernate.SessionFactory;

import org.hibernate.classic.Session;

import org.hibernate.cfg.*;

import org.hibernate.*;

import org.apache.log4j.*;

public class TestCase {

     /**

      * @param args

      */

     SessionFactory factory;

   

     public void createEmp(SalariedEmployee sm)

     {

      Session session=null;

      Transaction tx=null;

      try

      {

                 

                  session =factory.openSession();

                 

         

tx=session.beginTransaction();

       

                  System.out.println("break1 in cd");

                  session.save(sm);

                 

                  tx.commit();

                  System.out.println("record inserted");

      }

      catch(HibernateException e)

      {

               

     e.printStackTrace();

                 

      }

     }

     public static void main(String[] args) {

                 // TODO Auto-generated method stub

      System.out.println("first");

                 TestCase t=new TestCase();

                 Configuration cfg=new Configuration();

                 cfg.configure();

                 //cfg.addResource("employee.hbm.xml");

                 //cfg.addResource("personaldetails.hbm.xml");

                 System.out.println("break 2");

               

t.factory=cfg.buildSessionFactory();

                 SalariedEmployee se=new SalariedEmployee();

                 se.setEname("madhav");

                 se.setAnnualSal(2000);

                 t.createEmp(se);

System.out.println("execution over");

     }

}

Output- console:

Output-sql-prompt: