001 //$HeadURL: svn+ssh://rbezema@svn.wald.intevation.org/deegree/base/branches/2.2_testing/src/org/deegree/io/datastore/sql/TableAliasGenerator.java $
002 /*---------------- FILE HEADER ------------------------------------------
003
004 This file is part of deegree.
005 Copyright (C) 2001-2008 by:
006 EXSE, Department of Geography, University of Bonn
007 http://www.giub.uni-bonn.de/deegree/
008 lat/lon GmbH
009 http://www.lat-lon.de
010
011 This library is free software; you can redistribute it and/or
012 modify it under the terms of the GNU Lesser General Public
013 License as published by the Free Software Foundation; either
014 version 2.1 of the License, or (at your option) any later version.
015
016 This library is distributed in the hope that it will be useful,
017 but WITHOUT ANY WARRANTY; without even the implied warranty of
018 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
019 Lesser General Public License for more details.
020
021 You should have received a copy of the GNU Lesser General Public
022 License along with this library; if not, write to the Free Software
023 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
024
025 Contact:
026
027 Andreas Poth
028 lat/lon GmbH
029 Aennchenstraße 19
030 53177 Bonn
031 Germany
032 E-Mail: poth@lat-lon.de
033
034 Prof. Dr. Klaus Greve
035 Department of Geography
036 University of Bonn
037 Meckenheimer Allee 166
038 53115 Bonn
039 Germany
040 E-Mail: greve@giub.uni-bonn.de
041
042 ---------------------------------------------------------------------------*/
043 package org.deegree.io.datastore.sql;
044
045 /**
046 * Responsible for the generation of unique table aliases. This is needed in SQL queries in order to
047 * built joins that use the same table more than once.
048 *
049 * @author <a href="mailto:schneider@lat-lon.de">Markus Schneider </a>
050 * @author last edited by: $Author: apoth $
051 *
052 * @version $Revision: 9342 $, $Date: 2007-12-27 13:32:57 +0100 (Do, 27 Dez 2007) $
053 */
054 public class TableAliasGenerator {
055
056 private static String DEFAULT_PREFIX = "X";
057
058 private String prefix;
059
060 private int currentIdx = 1;
061
062 /**
063 * Creates a new <code>TableAliasGenerator</code> instance that uses a default prefix for
064 * generated table aliases.
065 */
066 public TableAliasGenerator() {
067 this.prefix = DEFAULT_PREFIX;
068 }
069
070 /**
071 * Creates a new <code>TableAliasGenerator</code> instance that uses the given prefix for
072 * generated table aliases.
073 *
074 * @param prefix
075 * prefix for generated table aliases
076 */
077 public TableAliasGenerator( String prefix ) {
078 this.prefix = prefix;
079 }
080
081 /**
082 * Returns a unique alias.
083 *
084 * @return a unique alias
085 */
086 public String generateUniqueAlias() {
087 return this.prefix
088 + this.currentIdx++;
089 }
090
091 /**
092 * Returns the specified number of unique aliases.
093 *
094 * @param n
095 * @return the specified number of unique aliases
096 */
097 public String[] generateUniqueAliases( int n ) {
098 String[] aliases = new String[n];
099 for (int i = 0; i < aliases.length; i++) {
100 aliases[i] = generateUniqueAlias();
101 }
102 return aliases;
103 }
104
105 /**
106 * Resets the alias sequence.
107 */
108 public void reset() {
109 this.currentIdx = 1;
110 }
111 }