VirtResSetIter.java

/*
 *  $Id$
 *
 *  This file is part of the OpenLink Software Virtuoso Open-Source (VOS)
 *  project.
 *
 *  Copyright (C) 1998-2012 OpenLink Software
 *
 *  This project 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; only version 2 of the License, dated June 1991.
 *
 *  This program 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 this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 *
 */

package virtuoso.jena.driver;

import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.NoSuchElementException;

import com.hp.hpl.jena.graph.Node;
import com.hp.hpl.jena.graph.Triple;
import com.hp.hpl.jena.graph.TripleMatch;
import com.hp.hpl.jena.shared.JenaException;
import com.hp.hpl.jena.util.iterator.NiceIterator;

public class VirtResSetIter extends NiceIterator<Triple> {
	protected ResultSet v_resultSet;
	protected Triple v_row;
	protected TripleMatch v_in;
	protected boolean v_finished = false;
	protected boolean v_prefetched = false;
	protected VirtGraph v_graph = null;
	protected PreparedStatement v_stmt = null;

	public VirtResSetIter() {
		v_finished = true;
	}

	public VirtResSetIter(VirtGraph graph, ResultSet resultSet, TripleMatch in,
			PreparedStatement stmt) {
		v_resultSet = resultSet;
		v_in = in;
		v_graph = graph;
		v_stmt = stmt;
	}

	public void reset(ResultSet resultSet, PreparedStatement sourceStatement) {
		v_resultSet = resultSet;
		v_finished = false;
		v_prefetched = false;
		v_row = null;
	}

	public boolean hasNext() {
		if (!v_finished && !v_prefetched)
			moveForward();
		return !v_finished;
	}

	public Triple removeNext() {
		Triple ret = next();
		remove();
		return ret;
	}

	public Triple next() {
		if (!v_finished && !v_prefetched)
			moveForward();

		v_prefetched = false;

		if (v_finished)
			throw new NoSuchElementException();

		return getRow();
	}

	public void remove() {
		if (v_row != null && v_graph != null) {
			v_graph.delete(v_row);
			v_row = null;
		}
	}

	protected void moveForward() {
		try {
			if (!v_finished && v_resultSet.next()) {
				extractRow();
				v_prefetched = true;
			} else
				close();
		} catch (Exception e) {
			throw new JenaException(e);
		}
	}

	protected void extractRow() throws Exception {
		Node NodeS, NodeP, NodeO;

		if (v_in.getMatchSubject() != null)
			NodeS = v_in.getMatchSubject();
		else
			NodeS = VirtGraph.Object2Node(v_resultSet.getObject("s"));

		if (v_in.getMatchPredicate() != null)
			NodeP = v_in.getMatchPredicate();
		else
			NodeP = VirtGraph.Object2Node(v_resultSet.getObject("p"));

		if (v_in.getMatchObject() != null)
			NodeO = v_in.getMatchObject();
		else
			NodeO = VirtGraph.Object2Node(v_resultSet.getObject("o"));

		v_row = new Triple(NodeS, NodeP, NodeO);
	}

	protected Triple getRow() {
		return v_row;
	}

	public void close() {
		if (!v_finished) {
			if (v_resultSet != null) {
				try {
					v_resultSet.close();
					v_stmt.close();
					v_resultSet = null;
					v_stmt = null;
				} catch (SQLException e) {
					throw new JenaException(e);
				}
			}
		}
		v_finished = true;
	}

	protected void finalize() throws SQLException {
		if (!v_finished && v_resultSet != null)
			close();
	}

}