    001    //$HeadURL: https://svn.wald.intevation.org/svn/deegree/base/branches/2.4_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    }