Exception in thread "main" org.hibernate.HibernateException: identifier of an instance of com.lmert.learnhib.CD was altered from 80 to 80
        at org.hibernate.event.def.DefaultFlushEntityEventListener.checkId(DefaultFlushEntityEventListener.java:58)
        at org.hibernate.event.def.DefaultFlushEntityEventListener.getValues(DefaultFlushEntityEventListener.java:157)
        at org.hibernate.event.def.DefaultFlushEntityEventListener.onFlushEntity(DefaultFlushEntityEventListener.java:113)
        at org.hibernate.event.def.AbstractFlushingEventListener.flushEntities(AbstractFlushingEventListener.java:195)
        at org.hibernate.event.def.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:76)
        at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:26)
        at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1000)
        at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:338)
        at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:106)
        at com.lmert.learnhib.Main.main(Main.java:55)

    Session session = getSession();
    session.beginTransaction();
   
    List l = session.createQuery(args[1]).list();
    int i;

    System.out.println(args[1]);
    System.out.println("--");

    for (i=0;i<l.size();i++) {
       System.out.println(l.get(i));
    }

    System.out.println("--");
    System.out.println(l.size()+" rows");

    session.getTransaction().commit();

CREATE TABLE CDs (
  id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
  artist VARCHAR(100),
  title VARCHAR(100)
);
CREATE TABLE CD_tracks (
  id INT NOT NULL,  -- this would be a foreign key, except that these are MyISAM tables
  trackNo INT NOT NULL,
  trackArtist VARCHAR(100),
  trackTitle VARCHAR(100),
  PRIMARY KEY(id,trackNo)
);

<hibernate-mapping>
    <class name="com.lmert.learnhib.CD" table="CDs"  >
   <id column="id" name="id"
       type="short" unsaved-value="0" access="field" >
       <generator class="identity"  />
   </id>

   <list name="tracks" access="field" table="CD_tracks"  >
       <key column="id" not-null="true" />
       <list-index
      column="trackNo"
      base="1"  />
       <composite-element class="com.lmert.learnhib.CDTrack" >
      <parent name="cd" />
      
      <property name="trackTitle" type="string" access="field" />
      <property name="trackArtist" type="string" access="field" />
      
       </composite-element>
   </list>
   
   <property name="artist" type="java.lang.String" access="field" />
   <property name="title" type="java.lang.String"  access="field" />
   
    </class>
</hibernate-mapping>

public class CD {

      /** An ID number in our collection. */
   private int id;

   private String artist;
   private String title;

   private List<CDTrack> tracks = new java.util.ArrayList();

      /** The ID is read-only to user code. */
   public int getId() {
      return id;   }

   public String getTitle() {
      return title;   }
   public void setTitle(String title) {
      this.title=title;   }

   public String getArtist() {
      return artist;   }
   public void setArtist(String artist) {
      this.artist=artist;   }


   public int hashCode() {
      return id;
   }


   public String toString() {
      return "CD#"+id+" \""+title+"\" ("+tracks.size()+" tracks)";
   }
}

public class CDTrack implements Serializable {

   private CD cd;
   private int trackNo;

   private String trackTitle;
   private String trackArtist;

   private void setCd(CD cd) {
      this.cd = cd;
   }
   private CD getCd() {
      return cd;
   }

   public CD getDisc() {
      return cd;
   }

   public String getTitle() {
      return trackTitle;   }

   public String getArtist() {
      return trackArtist;   }

   public void setTitle(String title) {
      trackTitle= title; }

   public void setArtist(String artist) {
      trackArtist= artist; }

}