Change Inheritance Type : Inheritance « JPA

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Java Tutorial » JPA » Inheritance

22. 16. 10. Change Inheritance Type

File: Employee.java


import java.util.Date;



import javax.persistence.Column;

import javax.persistence.DiscriminatorColumn;

import javax.persistence.Entity;

import javax.persistence.Id;

import javax.persistence.Inheritance;

import javax.persistence.InheritanceType;

import javax.persistence.Table;

import javax.persistence.Temporal;

import javax.persistence.TemporalType;



@Entity

@Table(name="EMP")

@Inheritance(strategy=InheritanceType.JOINED)

@DiscriminatorColumn(name="EMP_TYPE")

public abstract class Employee {

    @Id private int id;

    private String name;

    @Temporal(TemporalType.DATE)

    @Column(name="S_DATE")

    private Date startDate;





    public int getId() {

        return id;

    }

    

    public void setId(int id) {

        this.id = id;

    }

    

    public String getName() {

        return name;

    }

    

    public void setName(String name) {

        this.name = name;

    }



    public Date getStartDate() {

        return startDate;

    }



    public void setStartDate(Date startDate) {

        this.startDate = startDate;

    }



    public String toString() {

        return "Employee id: " + getId() + " name: " + getName();

    }

}



@Entity

@Table(name="COMPANY_EMP")

@Inheritance(strategy=InheritanceType.SINGLE_TABLE)

 abstract class CompanyEmployee extends Employee {

    private int vacation;





    public int getVacation() {

        return vacation;

    }



    public void setVacation(int vacation) {

        this.vacation = vacation;

    }

}



@Entity 

 class FullTimeEmployee extends CompanyEmployee {

    private long salary;

    @Column(name="PENSION")

    private long pensionContribution;

    

    public long getPensionContribution() {

        return pensionContribution;

    }

    

    public void setPensionContribution(long pension) {

        this.pensionContribution = pension;

    }

    

    public long getSalary() {

        return salary;

    }

    

    public void setSalary(long salary) {

        this.salary = salary;

    }



    public String toString() {

        return "FullTimeEmployee id: " + getId() + " name: " + getName();

    }

}



@Entity

 class PartTimeEmployee extends CompanyEmployee {

    @Column(name="H_RATE")

    private float hourlyRate;





    public float getHourlyRate() {

        return hourlyRate;

    }



    public void setHourlyRate(float hourlyRate) {

        this.hourlyRate = hourlyRate;

    }



    public String toString() {

        return "PartTimeEmployee id: " + getId() + " name: " + getName();

    }

}

File: Helper.java


import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.ResultSetMetaData;

import java.sql.Statement;



public class Helper {

  public static void checkData() throws Exception {

    Class.forName("org.hsqldb.jdbcDriver");

    Connection conn = DriverManager.getConnection("jdbc:hsqldb:data/tutorial", "sa", "");

    Statement st = conn.createStatement();



    ResultSet mrs = conn.getMetaData().getTables(null, null, null, new String[] { "TABLE" });

    while (mrs.next()) {

      String tableName = mrs.getString(3);

      System.out.println("\n\n\n\nTable Name: "+ tableName);



      ResultSet rs = st.executeQuery("select * from " + tableName);

      ResultSetMetaData metadata = rs.getMetaData();

      while (rs.next()) {

        System.out.println(" Row:");

        for (int i = 0; i < metadata.getColumnCount(); i++) {

          System.out.println("    Column Name: "+ metadata.getColumnLabel(i + 1)+ ",  ");

          System.out.println("    Column Type: "+ metadata.getColumnTypeName(i + 1)+ ":  ");

          Object value = rs.getObject(i + 1);

          System.out.println("    Column Value: "+value+"\n");

        }

      }

    }

  }

}

File: Main.java


import javax.persistence.EntityManager;

import javax.persistence.EntityManagerFactory;

import javax.persistence.Persistence;

import javax.persistence.Query;



public class Main {

  static EntityManagerFactory emf = Persistence.createEntityManagerFactory("JPAService");



  static EntityManager em = emf.createEntityManager();



  public static void main(String[] a) throws Exception {

    em.getTransaction().begin();



    FullTimeEmployee emp = new FullTimeEmployee();

    emp.setId(1);

    emp.setName("Tom");

    emp.setStartDate(new java.util.Date());

    emp.setPensionContribution(123);

    em.persist(emp);

    



    PartTimeEmployee emp1 = new PartTimeEmployee();

    emp1.setId(2);

    emp1.setName("Tom");

    emp1.setStartDate(new java.util.Date());

    emp1.setHourlyRate(123);

    em.persist(emp1);



    em.getTransaction().commit();

    em.close();

    emf.close();



    Helper.checkData();

  }

}

File: persistence.xml


<persistence xmlns="http://java.sun.com/xml/ns/persistence"

             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

             xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence" version="1.0">

  <persistence-unit name="JPAService" transaction-type="RESOURCE_LOCAL">

    <properties>

      <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>

      <property name="hibernate.hbm2ddl.auto" value="update"/>

      <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>

      <property name="hibernate.connection.username" value="sa"/>

      <property name="hibernate.connection.password" value=""/>

      <property name="hibernate.connection.url" value="jdbc:hsqldb:data/tutorial"/>

    </properties>

  </persistence-unit>

</persistence>

Download: JPA-ChangeInheritanceType.zip( 5,290 k)

22. 16. Inheritance
	22. 16. 1.	Persist subclass
	22. 16. 2.	Three Leve Entity Hierarchy
	22. 16. 3.	Set Discriminator Value In Subclass
	22. 16. 4.	Mark Discriminator Column For Entities In Hierarchy
	22. 16. 5.	Mark Abstract Entity With Inheritance
	22. 16. 6.	Inheritance Type TABLE_PER_CLASS
	22. 16. 7.	Inheritance Type JOINED
	22. 16. 8.	Discriminator Type: INTEGER
	22. 16. 9.	Discriminator Column And Discriminator Value
	22. 16. 10.	Change Inheritance Type
	22. 16. 11.	Add Properties In Abstract Entity
	22. 16. 12.	Adding Properties To SubClasses
	22. 16. 13.	Abstract Class As Mapped Superclass

Change Inheritance Type : Inheritance « JPA « Java Tutorial