Java/Hibernate/Class Hiearchy Mapping

Class Hierachy Mapping Table Per Class

/////////////////////////////////////////////////////////////////////////
<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE hibernate-mapping 
    PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN" 
    "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">
<hibernate-mapping> 
    <class name="Book" table="cd" discriminator-value="cd">
    <id name="id" type="integer"  unsaved-value="0">
      <generator class="increment"/>
    </id>
    <discriminator column="cd_type" type= "string"/>
    <property name="title"/>
    <property name="artist"/>
    <property name="purchasedate" type="date"/>
    <property name="cost" type="double"/>
    <subclass name="SpecialEditionBook" discriminator-value="SpecialEditionBook">
    <property name="newfeatures" type="string"/>
    </subclass>
    <subclass name="InternationalBook"
            discriminator-value="InternationalBook">
    <property name="languages"/>
    <property name="region"/>
    </subclass>
    </class>
  </hibernate-mapping>

/////////////////////////////////////////////////////////////////////////
import java.io.*;
import java.util.*;
  public class Book {
    int id;
    String title; 
    String artist;
    Date  purchaseDate; 
    double cost;
    public Book() {
    }
    public Book(String title, String artist, Date purchaseDate, double cost) {
      this.title = title;
      this.artist = artist;
      this.purchaseDate = purchaseDate;
      this.cost = cost;
    }
    public void setId(int id) { 
      this.id = id;
    }
    public int getId(){ 
      return id;
    }
    public void setTitle(String title) { 
      this.title = title;
    }
    public String getTitle() { 
      return title;
    }
    public void setArtist(String artist) { 
       this.artist = artist;
    }
    public String getArtist() { 
      return artist;
    }
    public void setPurchasedate(Date purchaseDate) { 
      this.purchaseDate = purchaseDate;
    }
    public Date getPurchasedate() { 
      return purchaseDate;
    }
    public void setCost(double cost) { 
      this.cost = cost;
    }
    public double getCost() { 
      return cost;
    }
  }
/////////////////////////////////////////////////////////////////////////
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
    "-//Hibernate/Hibernate Configuration DTD//EN"
    "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <!-- Database connection settings -->
        <property name="connection.driver_class">org.hsqldb.jdbcDriver</property>
        <property name="connection.url">jdbc:hsqldb:data/tutorial</property>
        <property name="connection.username">sa</property>
        <property name="connection.password"></property>
        <!-- JDBC connection pool (use the built-in) -->
        <property name="connection.pool_size">1</property>
        <!-- SQL dialect -->
        <property name="dialect">org.hibernate.dialect.HSQLDialect</property>
        <!-- Echo all executed SQL to stdout -->
        <property name="show_sql">true</property>
        <!-- Mapping files -->
        <mapping resource="Book.hbm.xml"/>
    </session-factory>
</hibernate-configuration>
/////////////////////////////////////////////////////////////////////////
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class HibernateUtil {
    public static final SessionFactory sessionFactory;
    static {
        try {
            // Create the SessionFactory from hibernate.cfg.xml
            sessionFactory = new Configuration().configure().buildSessionFactory();
        } catch (Throwable ex) {
            // Make sure you log the exception, as it might be swallowed
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }
    public static final ThreadLocal session = new ThreadLocal();
    public static Session currentSession() throws HibernateException {
        Session s = (Session) session.get();
        // Open a new Session, if this thread has none yet
        if (s == null) {
            s = sessionFactory.openSession();
            // Store it in the ThreadLocal variable
            session.set(s);
        }
        return s;
    }
    public static void closeSession() throws HibernateException {
        Session s = (Session) session.get();
        if (s != null)
            s.close();
        session.set(null);
    }
    
    static Connection conn; 
    static Statement st;
  public static void setup(String sql) {
    try {
      // Step 1: Load the JDBC driver.
      Class.forName("org.hsqldb.jdbcDriver");
      System.out.println("Driver Loaded.");
      // Step 2: Establish the connection to the database.
      String url = "jdbc:hsqldb:data/tutorial";
      conn = DriverManager.getConnection(url, "sa", "");
      System.out.println("Got Connection.");
      st = conn.createStatement();
      st.executeUpdate(sql);
    } catch (Exception e) {
      System.err.println("Got an exception! ");
      e.printStackTrace();
      System.exit(0);
    }
  }
  public static void checkData(String sql) {
    try {
      HibernateUtil.outputResultSet(st
          .executeQuery(sql));
//      conn.close();
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
    public static void outputResultSet(ResultSet rs) throws Exception{
    ResultSetMetaData metadata = rs.getMetaData();
    int numcols = metadata.getColumnCount();
    String[] labels = new String[numcols]; 
    int[] colwidths = new int[numcols];
    int[] colpos = new int[numcols];
    int linewidth;
      for (int i = 0; i < numcols; i++) {
        labels[i] = metadata.getColumnLabel(i + 1); // get its label
        System.out.print(labels[i]+"  ");
    }
      System.out.println("------------------------");
    while (rs.next()) {
        for (int i = 0; i < numcols; i++) {
        Object value = rs.getObject(i + 1);
        if(value == null){
            System.out.print("       ");
        }else{
            System.out.print(value.toString().trim()+"   ");
        }
        
      }
        System.out.println("       ");
    }
    }
}

/////////////////////////////////////////////////////////////////////////

import java.util.*;
public class InternationalBook extends Book { 
  private String languages; 
  private int region;
  
  public InternationalBook() {
  }
  public InternationalBook(String title, String artist, Date purchaseDate, double cost, String language, int region) {
    super(title, artist, purchaseDate, cost);
    languages = language;
    this.region = region;
  }
  public void setLanguages(String s) {
    languages = s;
  }
  public String getLanguages() {
    return languages;
  }
  public void setRegion(int i) {
    region = i;
  }
  public int getRegion() {
    return region;
  }
}

/////////////////////////////////////////////////////////////////////////
log4j.rootCategory=WARN, console
log4j.appender.console=org.apache.log4j.ConsoleAppender
log4j.appender.console.layout=org.apache.log4j.PatternLayout
log4j.appender.console.layout.ConversionPattern=%-4r [%t] %-5p %c %x - %m%n
log4j.appender.stdout.Target=System.out

/////////////////////////////////////////////////////////////////////////
import java.io.Serializable;
import java.util.*;
import org.hibernate.*;
import org.hibernate.cfg.*;
import org.hibernate.criterion.*;
import org.hibernate.event.*;
import org.hibernate.event.def.*;
public class Main {
   public static void main(String[] args) throws Exception {
      HibernateUtil.setup("create table cd(id int,title varchar,artist varchar,purchasedate date,cost double,newfeatures varchar,languages varchar,region int,cd_type varchar);");    

      Session session = HibernateUtil.currentSession();
      Book cd = new Book("Book", "R", new Date(), 9.99);
      SpecialEditionBook secd = new SpecialEditionBook("sBook", "R", new Date(), 9.99, "W");
      InternationalBook icd = new InternationalBook("IBook", "R", new Date(), 9.99, "S", 4);
      session.save(cd);
      session.save(secd);
      session.save(icd);
      session.flush();      
      session.close();
     HibernateUtil.checkData("select * from cd");
   }
}

/////////////////////////////////////////////////////////////////////////
import java.util.*;
public class SpecialEditionBook extends Book { 
  private String newfeatures;
  
  public SpecialEditionBook() {
  }
    public SpecialEditionBook(String title, String artist, Date purchaseDate, double cost, String features) {
      super(title, artist, purchaseDate, cost);
      newfeatures = features;
    }
  public void setNewfeatures(String s) {
    newfeatures = s;
  }
  public String getNewfeatures() {
    return newfeatures;
  }
}

Class Hierarchy Mapping Table Per Concrete Class

/////////////////////////////////////////////////////////////////////////
import java.io.*;
import java.util.*;
  public class Book {
    int id;
    String title; 
    String artist;
    Date  purchaseDate; 
    double cost;
    public Book() {
    }
    public Book(String title, String artist, Date purchaseDate, double cost) {
      this.title = title;
      this.artist = artist;
      this.purchaseDate = purchaseDate;
      this.cost = cost;
    }
    public void setId(int id) { 
      this.id = id;
    }
    public int getId(){ 
      return id;
    }
    public void setTitle(String title) { 
      this.title = title;
    }
    public String getTitle() { 
      return title;
    }
    public void setArtist(String artist) { 
       this.artist = artist;
    }
    public String getArtist() { 
      return artist;
    }
    public void setPurchasedate(Date purchaseDate) { 
      this.purchaseDate = purchaseDate;
    }
    public Date getPurchasedate() { 
      return purchaseDate;
    }
    public void setCost(double cost) { 
      this.cost = cost;
    }
    public double getCost() { 
      return cost;
    }
  }

/////////////////////////////////////////////////////////////////////////
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
    "-//Hibernate/Hibernate Configuration DTD//EN"
    "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <!-- Database connection settings -->
        <property name="connection.driver_class">org.hsqldb.jdbcDriver</property>
        <property name="connection.url">jdbc:hsqldb:data/tutorial</property>
        <property name="connection.username">sa</property>
        <property name="connection.password"></property>
        <!-- JDBC connection pool (use the built-in) -->
        <property name="connection.pool_size">1</property>
        <!-- SQL dialect -->
        <property name="dialect">org.hibernate.dialect.HSQLDialect</property>
        <!-- Echo all executed SQL to stdout -->
        <property name="show_sql">true</property>
        <!-- Mapping files -->
        <mapping resource="Book.hbm.xml"/>
    </session-factory>
</hibernate-configuration>

/////////////////////////////////////////////////////////////////////////
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class HibernateUtil {
    public static final SessionFactory sessionFactory;
    static {
        try {
            // Create the SessionFactory from hibernate.cfg.xml
            sessionFactory = new Configuration().configure().buildSessionFactory();
        } catch (Throwable ex) {
            // Make sure you log the exception, as it might be swallowed
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }
    public static final ThreadLocal session = new ThreadLocal();
    public static Session currentSession() throws HibernateException {
        Session s = (Session) session.get();
        // Open a new Session, if this thread has none yet
        if (s == null) {
            s = sessionFactory.openSession();
            // Store it in the ThreadLocal variable
            session.set(s);
        }
        return s;
    }
    public static void closeSession() throws HibernateException {
        Session s = (Session) session.get();
        if (s != null)
            s.close();
        session.set(null);
    }
    
    static Connection conn; 
    static Statement st;
  public static void setup(String sql) {
    try {
      // Step 1: Load the JDBC driver.
      Class.forName("org.hsqldb.jdbcDriver");
      System.out.println("Driver Loaded.");
      // Step 2: Establish the connection to the database.
      String url = "jdbc:hsqldb:data/tutorial";
      conn = DriverManager.getConnection(url, "sa", "");
      System.out.println("Got Connection.");
      st = conn.createStatement();
      st.executeUpdate(sql);
    } catch (Exception e) {
      System.err.println("Got an exception! ");
      e.printStackTrace();
      System.exit(0);
    }
  }
  public static void checkData(String sql) {
    try {
      HibernateUtil.outputResultSet(st
          .executeQuery(sql));
//      conn.close();
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
    public static void outputResultSet(ResultSet rs) throws Exception{
    ResultSetMetaData metadata = rs.getMetaData();
    int numcols = metadata.getColumnCount();
    String[] labels = new String[numcols]; 
    int[] colwidths = new int[numcols];
    int[] colpos = new int[numcols];
    int linewidth;
      for (int i = 0; i < numcols; i++) {
        labels[i] = metadata.getColumnLabel(i + 1); // get its label
        System.out.print(labels[i]+"  ");
    }
      System.out.println("------------------------");
    while (rs.next()) {
        for (int i = 0; i < numcols; i++) {
        Object value = rs.getObject(i + 1);
        if(value == null){
            System.out.print("       ");
        }else{
            System.out.print(value.toString().trim()+"   ");
        }
        
      }
        System.out.println("       ");
    }
    }
}

/////////////////////////////////////////////////////////////////////////
import java.util.*;
public class InternationalBook extends Book { 
  private String languages; 
  private int region;
  
  public InternationalBook() {
  }
  public InternationalBook(String title, String artist, Date purchaseDate, double cost, String language, int region) {
    super(title, artist, purchaseDate, cost);
    languages = language;
    this.region = region;
  }
  public void setLanguages(String s) {
    languages = s;
  }
  public String getLanguages() {
    return languages;
  }
  public void setRegion(int i) {
    region = i;
  }
  public int getRegion() {
    return region;
  }
}

/////////////////////////////////////////////////////////////////////////

import java.io.Serializable;
import java.util.*;
import org.hibernate.*;
import org.hibernate.cfg.*;
import org.hibernate.criterion.*;
import org.hibernate.event.*;
import org.hibernate.event.def.*;
public class Main {
   public static void main(String[] args) throws Exception {
      HibernateUtil.setup("create table cd(id int,title varchar,artist varchar,purchasedate date,cost double);");    
      HibernateUtil.setup("create table secd(id int,title varchar,artist varchar,purchasedate date,cost double,newfeatures varchar);");    
      HibernateUtil.setup("create table icd(id int,title varchar,artist varchar,purchasedate date,cost double,languages varchar,region int);");    

      Session session = HibernateUtil.currentSession();
      Book cd = new Book("Book", "R", new Date(), 9.99);
      SpecialEditionBook secd = new SpecialEditionBook("sBook", "R", new Date(), 9.99, "W");
      InternationalBook icd = new InternationalBook("IBook", "R", new Date(), 9.99, "S", 4);
      session.save(cd);
      session.save(secd);
      session.save(icd);
      session.flush();      
      session.close();
     HibernateUtil.checkData("select * from cd");
     HibernateUtil.checkData("select * from secd");
     HibernateUtil.checkData("select * from icd");
   }
}

/////////////////////////////////////////////////////////////////////////
import java.util.*;
public class SpecialEditionBook extends Book { 
  private String newfeatures;
  
  public SpecialEditionBook() {
  }
    public SpecialEditionBook(String title, String artist, Date purchaseDate, double cost, String features) {
      super(title, artist, purchaseDate, cost);
      newfeatures = features;
    }
  public void setNewfeatures(String s) {
    newfeatures = s;
  }
  public String getNewfeatures() {
    return newfeatures;
  }
}

/////////////////////////////////////////////////////////////////////////
<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE hibernate-mapping 
    PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN" 
    "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">
<hibernate-mapping> 
    <class name="Book" table="cd" discriminator-value="cd"> 
        <id name="id" type="integer" unsaved-value="0">
            <generator  class="increment"/>
        </id>
        <property name="title"/>
        <property name="artist"/>
        <property name="purchasedate" type="date"/> 
        <property name="cost" type="double"/> 
    </class>
    
    <class  name="SpecialEditionBook" table="secd">
        <id name="id" type="integer" unsaved-value="0">
            <generator  class="increment"/>
        </id>
        <property name="title"/>
        <property name="artist"/>
        <property name="purchasedate" type="date"/> 
        <property name="cost" type="double"/> 
        <property name="newfeatures" type="string"/>
    </class>
    
    <class  name="InternationalBook" table="icd">
        <id name="id" type="integer" unsaved-value="0">
            <generator  class="increment"/>
        </id>
        <property name="title"/>
        <property name="artist"/>
        <property name="purchasedate" type="date"/> 
        <property name="cost" type="double"/> 
        <property name="languages"/>
        <property name="region"/>
    </class> 
</hibernate-mapping>

/////////////////////////////////////////////////////////////////////////

ClassHierchy Mapping Table Per Sub class

/////////////////////////////////////////////////////////////////////////
<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE hibernate-mapping 
    PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN" 
    "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">
<hibernate-mapping> 
 <class name="Book"
         table="cd">
     <id name="id"
         type="integer"
         unsaved-value="0">
       <generator class="increment"/>
     </id>
  <property name="title"/>
         <property name="artist"/>
         <property name="purchasedate" type="date"/>
         <property name="cost" type="double"/>
  <joined-subclass name="SpecialEditionBook"
                   table="secd">
    <key column="id"/>
    <property name="newfeatures" type="string"/>
  </joined-subclass>
  <joined-subclass name="InternationalBook"
                   table="icd">
    <key column="id"/>
    <property name="languages"/>
    <property name="region"/>
  </joined-subclass>
  </class>
</hibernate-mapping>


/////////////////////////////////////////////////////////////////////////
import java.io.*;
import java.util.*;
  public class Book {
    int id;
    String title; 
    String artist;
    Date  purchaseDate; 
    double cost;
    public Book() {
    }
    public Book(String title, String artist, Date purchaseDate, double cost) {
      this.title = title;
      this.artist = artist;
      this.purchaseDate = purchaseDate;
      this.cost = cost;
    }
    public void setId(int id) { 
      this.id = id;
    }
    public int getId(){ 
      return id;
    }
    public void setTitle(String title) { 
      this.title = title;
    }
    public String getTitle() { 
      return title;
    }
    public void setArtist(String artist) { 
       this.artist = artist;
    }
    public String getArtist() { 
      return artist;
    }
    public void setPurchasedate(Date purchaseDate) { 
      this.purchaseDate = purchaseDate;
    }
    public Date getPurchasedate() { 
      return purchaseDate;
    }
    public void setCost(double cost) { 
      this.cost = cost;
    }
    public double getCost() { 
      return cost;
    }
  }
/////////////////////////////////////////////////////////////////////////
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
    "-//Hibernate/Hibernate Configuration DTD//EN"
    "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <!-- Database connection settings -->
        <property name="connection.driver_class">org.hsqldb.jdbcDriver</property>
        <property name="connection.url">jdbc:hsqldb:data/tutorial</property>
        <property name="connection.username">sa</property>
        <property name="connection.password"></property>
        <!-- JDBC connection pool (use the built-in) -->
        <property name="connection.pool_size">1</property>
        <!-- SQL dialect -->
        <property name="dialect">org.hibernate.dialect.HSQLDialect</property>
        <!-- Echo all executed SQL to stdout -->
        <property name="show_sql">true</property>
        <!-- Mapping files -->
        <mapping resource="Book.hbm.xml"/>
    </session-factory>
</hibernate-configuration>
/////////////////////////////////////////////////////////////////////////
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class HibernateUtil {
    public static final SessionFactory sessionFactory;
    static {
        try {
            // Create the SessionFactory from hibernate.cfg.xml
            sessionFactory = new Configuration().configure().buildSessionFactory();
        } catch (Throwable ex) {
            // Make sure you log the exception, as it might be swallowed
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }
    public static final ThreadLocal session = new ThreadLocal();
    public static Session currentSession() throws HibernateException {
        Session s = (Session) session.get();
        // Open a new Session, if this thread has none yet
        if (s == null) {
            s = sessionFactory.openSession();
            // Store it in the ThreadLocal variable
            session.set(s);
        }
        return s;
    }
    public static void closeSession() throws HibernateException {
        Session s = (Session) session.get();
        if (s != null)
            s.close();
        session.set(null);
    }
    
    static Connection conn; 
    static Statement st;
  public static void setup(String sql) {
    try {
      // Step 1: Load the JDBC driver.
      Class.forName("org.hsqldb.jdbcDriver");
      System.out.println("Driver Loaded.");
      // Step 2: Establish the connection to the database.
      String url = "jdbc:hsqldb:data/tutorial";
      conn = DriverManager.getConnection(url, "sa", "");
      System.out.println("Got Connection.");
      st = conn.createStatement();
      st.executeUpdate(sql);
    } catch (Exception e) {
      System.err.println("Got an exception! ");
      e.printStackTrace();
      System.exit(0);
    }
  }
  public static void checkData(String sql) {
    try {
      HibernateUtil.outputResultSet(st
          .executeQuery(sql));
//      conn.close();
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
    public static void outputResultSet(ResultSet rs) throws Exception{
    ResultSetMetaData metadata = rs.getMetaData();
    int numcols = metadata.getColumnCount();
    String[] labels = new String[numcols]; 
    int[] colwidths = new int[numcols];
    int[] colpos = new int[numcols];
    int linewidth;
      for (int i = 0; i < numcols; i++) {
        labels[i] = metadata.getColumnLabel(i + 1); // get its label
        System.out.print(labels[i]+"  ");
    }
      System.out.println("------------------------");
    while (rs.next()) {
        for (int i = 0; i < numcols; i++) {
        Object value = rs.getObject(i + 1);
        if(value == null){
            System.out.print("       ");
        }else{
            System.out.print(value.toString().trim()+"   ");
        }
        
      }
        System.out.println("       ");
    }
    }
}

/////////////////////////////////////////////////////////////////////////

import java.util.*;
public class InternationalBook extends Book { 
  private String languages; 
  private int region;
  
  public InternationalBook() {
  }
  public InternationalBook(String title, String artist, Date purchaseDate, double cost, String language, int region) {
    super(title, artist, purchaseDate, cost);
    languages = language;
    this.region = region;
  }
  public void setLanguages(String s) {
    languages = s;
  }
  public String getLanguages() {
    return languages;
  }
  public void setRegion(int i) {
    region = i;
  }
  public int getRegion() {
    return region;
  }
}

/////////////////////////////////////////////////////////////////////////
log4j.rootCategory=WARN, console
log4j.appender.console=org.apache.log4j.ConsoleAppender
log4j.appender.console.layout=org.apache.log4j.PatternLayout
log4j.appender.console.layout.ConversionPattern=%-4r [%t] %-5p %c %x - %m%n
log4j.appender.stdout.Target=System.out

/////////////////////////////////////////////////////////////////////////
import java.io.Serializable;
import java.util.*;
import org.hibernate.*;
import org.hibernate.cfg.*;
import org.hibernate.criterion.*;
import org.hibernate.event.*;
import org.hibernate.event.def.*;
public class Main {
   public static void main(String[] args) throws Exception {
      HibernateUtil.setup("create table cd(id int,title varchar,artist varchar,purchasedate date,cost double);");    
      HibernateUtil.setup("create table secd(id int,newfeatures varchar);");    
      HibernateUtil.setup("create table icd(id int,languages varchar,region int);");    
      Session session = HibernateUtil.currentSession();
      Book cd = new Book("Book", "R", new Date(), 9.99);
      SpecialEditionBook secd = new SpecialEditionBook("sBook", "R", new Date(), 9.99, "W");
      InternationalBook icd = new InternationalBook("IBook", "R", new Date(), 9.99, "S", 4);
      session.save(cd);
      session.save(secd);
      session.save(icd);
      session.flush();      
      session.close();
     HibernateUtil.checkData("select * from cd");
   }
}

/////////////////////////////////////////////////////////////////////////
import java.util.*;
public class SpecialEditionBook extends Book { 
  private String newfeatures;
  
  public SpecialEditionBook() {
  }
    public SpecialEditionBook(String title, String artist, Date purchaseDate, double cost, String features) {
      super(title, artist, purchaseDate, cost);
      newfeatures = features;
    }
  public void setNewfeatures(String s) {
    newfeatures = s;
  }
  public String getNewfeatures() {
    return newfeatures;
  }
}