001: //$HeadURL: https://svn.wald.intevation.org/svn/deegree/base/trunk/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 04:32:57 -0800 (Thu, 27 Dec 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 + this .currentIdx++;
088: }
089:
090: /**
091: * Returns the specified number of unique aliases.
092: *
093: * @param n
094: * @return the specified number of unique aliases
095: */
096: public String[] generateUniqueAliases(int n) {
097: String[] aliases = new String[n];
098: for (int i = 0; i < aliases.length; i++) {
099: aliases[i] = generateUniqueAlias();
100: }
101: return aliases;
102: }
103:
104: /**
105: * Resets the alias sequence.
106: */
107: public void reset() {
108: this .currentIdx = 1;
109: }
110: }
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