<hibernate-mapping>
  <class name="Task" table="tasks">
    <id name="id" column="task_id" type="long" unsaved-value="null">
      <generator class="native"/>
    </id>   
    <property name="name" column="task_name" type="string" length="30" not-null="true"/>
    <property name="code" column="task_code" type="string" length="30" not-null="true"/>
    <property name="expirationDate" column="task_expirationDate" type="java.sql.Date" not-null="true"/>
    <set name="taskAttributes" table="taskAttributes" cascade="all" inverse="true" lazy="true">
      <key column="task_id"/>
      <one-to-many class="TaskAttribute"/>
    </set>
  </class>
</hibernate-mapping>

<hibernate-mapping>
  <class name="TaskAttribute" table="taskAttributes">
     <id name="id" column="taskAttribute_id" type="long" unsaved-value="null">
      <generator class="native"/>
    </id>
    <property name="expirationDate" column="taskAttribute_expirationDate" type="java.sql.Date" not-null="true"/>
    <many-to-one name="task" class="Task" column="task_id" not-null="true" cascade="all"/>
    <one-to-one name="attribute" class="Attribute" column="attribute_id" not-null="true"/>
  </class>
</hibernate-mapping>

<hibernate-mapping>
  <class name="Attribute" table="attributes">
    <id name="id" column="attribute_id" type="long" unsaved-value="null">   
      <generator class="native"/>
    </id>
    <property name="name" column="attribute_name" type="string" length="30" not-null="true"/>
    <property name="expirationDate" column="attribute_expirationDate" type="java.sql.Date" not-null="true"/>
  </class>
</hibernate-mapping>

net.sf.hibernate.HibernateException: SQL insert, update or delete failed (row not found)
        at net.sf.hibernate.impl.NonBatchingBatcher.addToBatch(NonBatchingBatcher.java:25)
        at net.sf.hibernate.persister.EntityPersister.update(EntityPersister.java:687)
        at net.sf.hibernate.persister.EntityPersister.update(EntityPersister.java:640)
        at net.sf.hibernate.impl.ScheduledUpdate.execute(ScheduledUpdate.java:52)
        at net.sf.hibernate.impl.SessionImpl.executeAll(SessionImpl.java:2407)
        at net.sf.hibernate.impl.SessionImpl.execute(SessionImpl.java:2361)
        at net.sf.hibernate.impl.SessionImpl.flush(SessionImpl.java:2229)
        at net.sf.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:61)
        at Test.main(Test.java:51)
Exception in thread "main" net.sf.hibernate.HibernateException: SQL insert, update or delete failed (row not found)
        at net.sf.hibernate.impl.NonBatchingBatcher.addToBatch(NonBatchingBatcher.java:25)
        at net.sf.hibernate.persister.EntityPersister.update(EntityPersister.java:687)
        at net.sf.hibernate.persister.EntityPersister.update(EntityPersister.java:640)
        at net.sf.hibernate.impl.ScheduledUpdate.execute(ScheduledUpdate.java:52)
        at net.sf.hibernate.impl.SessionImpl.executeAll(SessionImpl.java:2407)
        at net.sf.hibernate.impl.SessionImpl.execute(SessionImpl.java:2361)
        at net.sf.hibernate.impl.SessionImpl.flush(SessionImpl.java:2229)
        at net.sf.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:61)
        at Test.main(Test.java:51)

public class Attribute {

   private long id;
   private String name;
   private Date expirationDate;
   
   public Attribute() {
   }
   
   
   public Date getExpirationDate() {
      return expirationDate;
   }

   public long getId() {
      return id;
   }

   public String getName() {
      return name;
   }

   public void setExpirationDate(Date date) {
      expirationDate = date;
   }

   public void setId(long l) {
      id = l;
   }

   public void setName(String string) {
      name = string;
   }

}

public class Task {
   
   private long id;
   private String name;
   private String code;
   private Date expirationDate;
   private Set taskAttributes = new TreeSet();
   
   public Task() {
   }
   
   public String getCode() {
      return code;
   }

   public Date getExpirationDate() {
      return expirationDate;
   }

   public long getId() {
      return id;
   }

   public String getName() {
      return name;
   }

   public Set getTaskAttributes() {
      return taskAttributes;
   }

   public void setCode(String string) {
      code = string;
   }

   public void setExpirationDate(Date date) {
      expirationDate = date;
   }

   public void setId(long l) {
      id = l;
   }

   public void setName(String string) {
      name = string;
   }

   public void setTaskAttributes(Set list) {
      taskAttributes = list;
   }
   
   public void addTaskAttribute(Attribute attribute) {
      TaskAttribute taskAttribute = new TaskAttribute();
      taskAttribute.setAttribute(attribute);
      taskAttribute.setTask(this);
      taskAttribute.setExpirationDate(new Date(20040512));
      getTaskAttributes().add(taskAttribute);
   }
}

public class TaskAttribute {
   
   private long id;
   private Date expirationDate;
   private Attribute attribute;
   private Task task;
   
   public TaskAttribute() {
   }
   
   public Attribute getAttribute() {
      return attribute;
   }

   public Date getExpirationDate() {
      return expirationDate;
   }

   public void setAttribute(Attribute attribute) {
      this.attribute = attribute;
   }

   public void setExpirationDate(Date date) {
      expirationDate = date;
   }

   public long getId() {
      return id;
   }

   public Task getTask() {
      return task;
   }

   public void setId(long l) {
      id = l;
   }

   public void setTask(Task task) {
      this.task = task;
   }

}

public class Test {

   public static void main(String [] args) throws Exception {
      
      Task task = new Task();
      task.setName("cucho");
      task.setCode("abc");
      task.setExpirationDate(new Date(20040512));
      
      Attribute attribute = new Attribute();
      attribute.setName("cuchoAttribute");
      attribute.setExpirationDate(new Date(20040512));
      
      task.addTaskAttribute(attribute);
      
      Configuration cfg = new Configuration().addClass(Task.class).addClass(TaskAttribute.class).addClass(Attribute.class);
      SessionFactory sf = cfg.buildSessionFactory();
      Session session = sf.openSession();
      
      Transaction t = session.beginTransaction();
      
      session.save(attribute);
      //session.save(taskAttribute);
      session.flush();
      session.saveOrUpdate(task);
      
      t.commit();
      session.close();
   }
}