Abstract Class As Mapped Superclass : Inheritance « JPA « Java Tutorial

1. Java Tutorial
2. JPA
3. Inheritance

File: Customer.java

import java.io.Serializable;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.DiscriminatorColumn;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
import javax.persistence.JoinColumn;
import javax.persistence.MappedSuperclass;
import javax.persistence.OneToOne;
import javax.persistence.Table;
import javax.persistence.Version;

@Entity
@Table(name = "ADDRESS")
class Address implements Serializable {
  protected String city;

  @Id
  protected Long id;



  @Version
  protected Long version;

  @Column(name = "ZIP_CODE")
  protected Long zipCode;

  public Address() {
  }

  public String getCity() {
    return city;
  }

  public void setCity(String city) {
    this.city = city;
  }

  public void setId(Long id) {
    this.id = id;
  }

  public Long getId() {
    return id;
  }
  public Long getZipCode() {
    return zipCode;
  }

  public void setZipCode(Long zipCode) {
    this.zipCode = zipCode;
  }
}

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
@DiscriminatorColumn(name = "TYPE")
class Employee extends Person implements Serializable {
  protected String email;

  protected String dept;

  public Employee() {
  }

  public String getEmail() {
    return email;
  }

  public void setEmail(String email) {
    this.email = email;
  }

  public String getDept() {
    return dept;
  }

  public void setDept(String dept) {
    this.dept = dept;
  }
}

@MappedSuperclass
abstract class Person implements Serializable {


  @OneToOne(cascade = { CascadeType.ALL })
  @JoinColumn(name = "HOME_ADDRESS", referencedColumnName = "ID")
  private Address homeAddress;

  @Id
  @Column(nullable = false)
  @GeneratedValue(generator = "PersonIdGenerator")
  private Long id;


  @Version
  private Long version;

  public Person() {
  }
  public Address getHomeAddress() {
    return homeAddress;
  }

  public void setHomeAddress(Address homeAddress) {
    this.homeAddress = homeAddress;
  }

  public Long getId() {
    return id;
  }

  public void setId(Long id) {
    this.id = id;
  }

}

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 java.util.List;

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();


    Customer cus = new Customer();
    
    cus.setFirstName("asdf");
    
    em.persist(cus);

    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>

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