Java tutorial
/* This file is part of Cyclos (www.cyclos.org). A project of the Social Trade Organisation (www.socialtrade.org). Cyclos is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. Cyclos is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with Cyclos; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ package nl.strohalm.cyclos.utils; import java.io.Closeable; import java.util.Iterator; import nl.strohalm.cyclos.utils.conversion.Transformer; import org.hibernate.Query; import org.hibernate.SQLQuery; import org.hibernate.ScrollMode; import org.hibernate.ScrollableResults; /** * Wraps a Hibernate ScrollableResults in an iterator * * @author luis */ public class ScrollableResultsIterator<T> implements Iterator<T>, Closeable { private ScrollableResults results; private T nextObject; private Transformer<Object[], T> transformer; private boolean array; public ScrollableResultsIterator(final Query query, final Transformer<Object[], T> transformer) { this.results = query.scroll(ScrollMode.FORWARD_ONLY); if (query instanceof SQLQuery) { // The getReturnTypes doesn't work for SQLQueries... Assume an array array = true; } else { // this (extra) check to see if the query starts with "select new" is just to support the // following case: SELECT new A(e.prop1, e.prop2) FROM Entity e ... // in that case we musn't return an array in the next() method. array = query.getReturnTypes().length > 1 && !query.getQueryString().trim().toLowerCase().startsWith("select new"); } this.transformer = transformer; getNextObject(); DataIteratorHelper.registerOpen(this, true); } //@Override public void close() { results.close(); } //@Override public boolean hasNext() { return nextObject != null; } //@Override public T next() { final T currentObject = nextObject; getNextObject(); return currentObject; } //@Override public void remove() { throw new UnsupportedOperationException(); } @SuppressWarnings("unchecked") private void getNextObject() { if (results.next()) { if (transformer != null) { nextObject = transformer.transform(results.get()); } else { nextObject = (T) (array ? results.get() : results.get(0)); } } else { nextObject = null; } } }