001 //$HeadURL: svn+ssh://jwilden@svn.wald.intevation.org/deegree/base/branches/2.5_testing/src/org/deegree/io/GenericSQLIDGenerator.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;
037
038 import java.sql.Connection;
039 import java.sql.ResultSet;
040 import java.sql.SQLException;
041 import java.sql.Statement;
042
043 import org.deegree.framework.util.DataBaseIDGenerator;
044
045 /**
046 * Primary key generator for generic JDBC-connections.
047 * <p>
048 * NOTE: At the moment, every application has to take care of locking the table to prevent problems
049 * in multithreaded or multihosted applications.
050 * <p>
051 *
052 * @author <a href="mailto:mschneider@lat-lon.de">Markus Schneider</a>
053 * @version $Revision: 18195 $ $Date: 2009-06-18 17:55:39 +0200 (Do, 18 Jun 2009) $
054 */
055 class GenericSQLIDGenerator implements DataBaseIDGenerator {
056
057 Connection con;
058
059 int fieldType;
060
061 boolean isNumeric;
062
063 String tableName;
064
065 String fieldName;
066
067 /**
068 * Constructs a new GenericSQLIDGenerator.
069 * <p>
070 *
071 * @param con
072 * @param fieldType
073 */
074 GenericSQLIDGenerator( Connection con, String tableName, String fieldName, int fieldType, boolean isNumeric ) {
075 this.con = con;
076 this.fieldName = fieldName;
077 this.tableName = tableName;
078 this.fieldType = fieldType;
079 this.isNumeric = isNumeric;
080 }
081
082 /**
083 * Returns the successor to the given id (string). Valid characters in the id-string are: 0-9,
084 * a-z, A-Z. Every other character may result in an exception.
085 * <p>
086 *
087 * @param lastId
088 * @return the successor to the given id (string).
089 */
090 private String incrementId( String lastId ) {
091 char[] chars = lastId.toCharArray();
092 for ( int i = chars.length - 1; i >= 0; i-- ) {
093 char c = chars[i];
094 if ( c >= '0' && c <= '9' ) {
095 if ( c == '9' ) {
096 c = 'a';
097 } else {
098 c++;
099 }
100 } else if ( c >= 'a' && c <= 'z' ) {
101 if ( c == 'z' ) {
102 c = 'A';
103 } else {
104 c++;
105 }
106 } else if ( c >= 'A' && c <= 'Z' ) {
107 if ( c == 'Z' ) {
108 c = '0';
109 } else {
110 c++;
111 }
112 }
113 chars[i] = c;
114 if ( c != '0' ) {
115 break;
116 }
117 }
118 String newId = new String( chars );
119 if ( chars[0] == '0' ) {
120 newId = '1' + newId;
121 }
122 return newId;
123 }
124
125 /**
126 * Generates a new id, suitable as a primary key for the next dataset.
127 * <p>
128 *
129 * @return Id, the object type depends on the database field used as primary key
130 */
131 public Object generateUniqueId()
132 throws SQLException {
133
134 Object id = null;
135
136 // retrieve last id
137 Statement stmt = con.createStatement();
138 ResultSet rs = stmt.executeQuery( "SELECT MAX(" + fieldName + ") FROM " + tableName );
139
140 if ( rs.next() ) {
141 if ( isNumeric ) {
142 id = new Integer( rs.getInt( 1 ) + 1 );
143 } else {
144 String oldId = rs.getString( 1 );
145 if ( oldId != null ) {
146 id = incrementId( oldId );
147 } else {
148 id = "0";
149 }
150 }
151 } else {
152 if ( isNumeric ) {
153 id = new Integer( 0 );
154 } else {
155 id = "0";
156 }
157 }
158 rs.close();
159 stmt.close();
160 return id;
161 }
162 }