<class name="A" table="a" >
<id name="id" column="ot_id" >
   <generator class="native">
   <param name="sequence">a_seq_id</param>
   </generator>
</id>
<natural-id >
<many-to-one name="b" class="B" column="b" access="property"  />
<many-to-one name="c" class="C" column="c" access="property" />
<many-to-one name="d" class="D" column="d" access="property" />
</natural-id>

<property name="number" column="nr" />
</class>

<class name="de.informaticum.orm.hibernate.test.EntityA" table="entityA" >
<id name="id" column="id" type="java.lang.Long" unsaved-value="-1">
      <generator class="native">
         <param name="sequence">entitya_seq</param>
      </generator>
   </id>
   <natural-id >
      <property name="uniquekey1" />
      <property name="uniquekey2" />
   </natural-id>
   
   <property name="nonunique" />
</class>

public class EntityManager {
    private static final Logger log = Logger.getLogger(EntityManager.class);
   
    HibernateTemplate ht= null;
   
    public EntityManager(HibernateTemplate tm) {
        this.ht = tm;
    }
    // load the last Row of the DB-Table
    public EntityA loadLastRow() {
        List<EntityA> list=null;
        try {
            list = ht.find("from EntityA a");
        } catch (DataAccessException e) {
            log.error(e.getMessage());
        }
        if (list!=null && list.size()>0) {
            return list.get(list.size()-1);
        }
        return null;
    }
    // merge the EntityA to the DB and get an actual instance.
    public EntityA merge(EntityA entity) {
        try {
            return (EntityA) ht.merge(entity);
        } catch (DataAccessException e) {
            log.error(e.getMessage());
            return null;
        }
    } 
}

public class TestMain {
    /**
     * @author Martin Sachs
     * @since 24.05.2006
     * @param args
     */
    public static void main(String[] args) {
       
        ...

        HibernateTemplate ht = null;
        ...
        // getting the hibernateTemplate here
        ...
           
            EntityManager manager = new EntityManager(ht );
           
            // create new Object
            EntityA entity = new EntityA(1L,new Date().getTime(),"value");
            // store Object to DB
            manager.merge(entity);
           
            // get last row
            EntityA loadedEntity = manager.loadLastRow();
            if (loadedEntity!=null) {
                System.out.println(loadedEntity.toString());
            }else {
                System.out.println("no row fetched");
            }
           
            if (loadedEntity!=null) {
                // modify Object
                loadedEntity.setNonunique("changed value");
                // setting id to -1, because it could be transient or generated
                // by someone manually

--->         loadedEntity.setId(-1L); <<---- here is my problem

I want to the the ID to -1  but i want to update the DB-Row with a merge.


                // store modified entity
                System.out.println("Store modified entity");
                EntityA storedEntity = manager.merge(loadedEntity);
                if (storedEntity!=null) {
                    System.out.print("modification stored: ");
                    System.out.println(loadedEntity.toString());
                }else {
                    System.out.println("modification not stored");
                }
            }
           
            ...
        }
    }
}

public class EntityA implements java.io.Serializable{
    private transient Long id = -1L;
    private Long uniquekey1;
    private Long uniquekey2;
    private String nonunique;
    ...
    // getter and setter
    ...
}

List oldDB = hibernateTemplate.find("from A a");

for(Object o1: newDB){
  for(Object o: oldDB){
     if (o1.equals(o)){
       o1.setID(o.getID());
     }
  }
}

  public Object getWithNaturalId(Object newEntity,SessionFactory factory) throws Exception{
   
    Object persisted=null;

    Class entityClass = newEntity.getClass();
    ClassMetadata meta = factory.getClassMetadata(entityClass);

    int[] nIdxs = meta.getNaturalIdentifierProperties();

    if (nIdxs != null && nIdxs.length > 0) {

      Session session = factory.openSession();
      Criteria crit = session.createCriteria(entityClass);

      for (int j = 0; j < nIdxs.length; j++) {

        String name = meta.getPropertyNames()[n[j]];
        Object value = PropertyUtils.getProperty(newEntity, name);

        crit.add(Restrictions.eq(name, value));
      }

       persisted = crit.uniqueResult();
     
    }
    return persisted;
   
  }