001    //$HeadURL: svn+ssh://jwilden@svn.wald.intevation.org/deegree/base/branches/2.5_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    }