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 }