    001    //$HeadURL: https://svn.wald.intevation.org/svn/deegree/base/branches/2.4_testing/src/org/deegree/io/datastore/sql/TableAliasGenerator.java $
    002    /*----------------------------------------------------------------------------
    003     This file is part of deegree, http://deegree.org/
    004     Copyright (C) 2001-2009 by:
    005       Department of Geography, University of Bonn
    006     and
    007       lat/lon GmbH
    008
    009     This library is free software; you can redistribute it and/or modify it under
    010     the terms of the GNU Lesser General Public License as published by the Free
    011     Software Foundation; either version 2.1 of the License, or (at your option)
    012     any later version.
    013     This library is distributed in the hope that it will be useful, but WITHOUT
    014     ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
    015     FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
    016     details.
    017     You should have received a copy of the GNU Lesser General Public License
    018     along with this library; if not, write to the Free Software Foundation, Inc.,
    019     59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
    020
    021     Contact information:
    022
    023     lat/lon GmbH
    024     Aennchenstr. 19, 53177 Bonn
    025     Germany
    026     http://lat-lon.de/
    027
    028     Department of Geography, University of Bonn
    029     Prof. Dr. Klaus Greve
    030     Postfach 1147, 53001 Bonn
    031     Germany
    032     http://www.geographie.uni-bonn.de/deegree/
    033
    034     e-mail: info@deegree.org
    035    ----------------------------------------------------------------------------*/
    036    package org.deegree.io.datastore.sql;
    037
    038    /**
    039     * Responsible for the generation of unique table aliases. This is needed in SQL queries in order to
    040     * built joins that use the same table more than once.
    041     *
    042     * @author <a href="mailto:schneider@lat-lon.de">Markus Schneider </a>
    043     * @author last edited by: $Author: mschneider $
    044     *
    045     * @version $Revision: 18195 $, $Date: 2009-06-18 17:55:39 +0200 (Do, 18. Jun 2009) $
    046     */
    047    public class TableAliasGenerator {
    048
    049        private static String DEFAULT_PREFIX = "X";
    050
    051        private String prefix;
    052
    053        private int currentIdx = 1;
    054
    055        /**
    056         * Creates a new <code>TableAliasGenerator</code> instance that uses a default prefix for
    057         * generated table aliases.
    058         */
    059        public TableAliasGenerator() {
    060            this.prefix = DEFAULT_PREFIX;
    061        }
    062
    063        /**
    064         * Creates a new <code>TableAliasGenerator</code> instance that uses the given prefix for
    065         * generated table aliases.
    066         *
    067         * @param prefix
    068         *            prefix for generated table aliases
    069         */
    070        public TableAliasGenerator( String prefix ) {
    071            this.prefix = prefix;
    072        }
    073
    074        /**
    075         * Returns a unique alias.
    076         *
    077         * @return a unique alias
    078         */
    079        public String generateUniqueAlias() {
    080            return this.prefix
    081                + this.currentIdx++;
    082        }
    083
    084        /**
    085         * Returns the specified number of unique aliases.
    086         *
    087         * @param n
    088         * @return the specified number of unique aliases
    089         */
    090        public String[] generateUniqueAliases( int n ) {
    091            String[] aliases = new String[n];
    092            for (int i = 0; i < aliases.length; i++) {
    093                aliases[i] = generateUniqueAlias();
    094            }
    095            return aliases;
    096        }
    097
    098        /**
    099         * Resets the alias sequence.
    100         */
    101        public void reset() {
    102            this.currentIdx = 1;
    103        }
    104    }