001    /*
002     *  Licensed to the Apache Software Foundation (ASF) under one
003     *  or more contributor license agreements.  See the NOTICE file
004     *  distributed with this work for additional information
005     *  regarding copyright ownership.  The ASF licenses this file
006     *  to you under the Apache License, Version 2.0 (the
007     *  "License"); you may not use this file except in compliance
008     *  with the License.  You may obtain a copy of the License at
009     *  
010     *    http://www.apache.org/licenses/LICENSE-2.0
011     *  
012     *  Unless required by applicable law or agreed to in writing,
013     *  software distributed under the License is distributed on an
014     *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015     *  KIND, either express or implied.  See the License for the
016     *  specific language governing permissions and limitations
017     *  under the License. 
018     *  
019     */
020    package org.apache.directory.shared.ldap.schema.comparators;
021    
022    
023    import org.apache.directory.shared.ldap.schema.LdapComparator;
024    import org.slf4j.Logger;
025    import org.slf4j.LoggerFactory;
026    
027    
028    /**
029     * A comparator for Strings.
030     * 
031     * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
032     * @version $Rev$
033     */
034    public class StringComparator extends LdapComparator<String>
035    {
036        /** A logger for this class */
037        private static final Logger LOG = LoggerFactory.getLogger( StringComparator.class );
038    
039        /** The serialVersionUID */
040        private static final long serialVersionUID = 1L;
041    
042        /**
043         * The StringComparator constructor. Its OID is the StringMatch matching
044         * rule OID.
045         */
046        public StringComparator( String oid )
047        {
048            super( oid );
049        }
050    
051        /**
052         * @see java.util.Comparator#compare(java.lang.Object, java.lang.Object)
053         */
054        public int compare( String s1, String s2 )
055        {
056            LOG.debug( "comparing String objects '{}' with '{}'", s1, s2 );
057            
058            // -------------------------------------------------------------------
059            // Handle some basis cases
060            // -------------------------------------------------------------------
061            if ( s1 == null )
062            {
063                return ( s2 == null ) ? 0 : -1;
064            }
065            
066            if ( s2 == null )
067            {
068                return 1;
069            }
070            
071            return s1.compareTo( s2 );
072        }
073    }