public static IdentifierGenerator create(String strategy,
    Type type,
    Properties params,
    Dialect dialect) throws MappingException 
{
		try {
			Class clazz = getIdentifierGeneratorClass( strategy, dialect );
			IdentifierGenerator idgen = ( IdentifierGenerator ) clazz.newInstance();
			if ( idgen instanceof Configurable ) {
				( ( Configurable ) idgen ).configure( type, params, dialect );
			}
			return idgen;
		}
		catch ( Exception e ) {
			throw new MappingException(
					"could not instantiate id generator [entity-name=" + params.get(
							IdentifierGenerator.ENTITY_NAME
					) + "]", e
			);
		}
}

 public static Number createNumber(long value,
    Class clazz) throws IdentifierGenerationException 
{
		if ( clazz == Long.class ) {
			return new Long( value );
		}
		else if ( clazz == Integer.class ) {
			return new Integer( ( int ) value );
		}
		else if ( clazz == Short.class ) {
			return new Short( ( short ) value );
		}
		else {
			throw new IdentifierGenerationException( "this id generator generates long, integer, short" );
		}
}

 public static Serializable get(ResultSet rs,
    Type type) throws SQLException, IdentifierGenerationException 
{
		Class clazz = type.getReturnedClass();
		if ( clazz == Long.class ) {
			return new Long( rs.getLong( 1 ) );
		}
		else if ( clazz == Integer.class ) {
			return new Integer( rs.getInt( 1 ) );
		}
		else if ( clazz == Short.class ) {
			return new Short( rs.getShort( 1 ) );
		}
		else if ( clazz == String.class ) {
			return rs.getString( 1 );
		}
		else {
			throw new IdentifierGenerationException( "this id generator generates long, integer, short or string" );
		}
}

 public static Serializable getGeneratedIdentity(ResultSet rs,
    Type type) throws SQLException, HibernateException 
{
		if ( !rs.next() ) {
			throw new HibernateException( "The database returned no natively generated identity value" );
		}
		final Serializable id = IdentifierGeneratorFactory.get( rs, type );
		if ( log.isDebugEnabled() ) {
			log.debug( "Natively generated identity: " + id );
		}
		return id;
}

Get the generated identifier when using identity columns

 public static Class getIdentifierGeneratorClass(String strategy,
    Dialect dialect) 
{
		Class clazz = ( Class ) GENERATORS.get( strategy );
		if ( "native".equals( strategy ) ) {
			clazz = dialect.getNativeIdentifierGeneratorClass();
		}
		try {
			if ( clazz == null ) {
				clazz = ReflectHelper.classForName( strategy );
			}
		}
		catch ( ClassNotFoundException e ) {
			throw new MappingException( "could not interpret id generator strategy: " + strategy );
		}
		return clazz;
}