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 java.text.ParseException;
024 import java.util.Comparator;
025
026 import org.apache.directory.shared.ldap.schema.parsers.AbstractSchemaDescription;
027 import org.apache.directory.shared.ldap.schema.parsers.NormalizerDescriptionSchemaParser;
028
029
030 /**
031 * A comparator for Normalizers. We compare the OIDs.
032 *
033 *
034 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
035 * @version $Rev$
036 */
037 public class NormalizerComparator implements Comparator<String>
038 {
039 /** A static instance of this comparator */
040 public static final Comparator<String> INSTANCE = new NormalizerComparator();
041
042 /** A parser for the Normalizers */
043 private static final NormalizerDescriptionSchemaParser normalizerParser =
044 new NormalizerDescriptionSchemaParser();
045
046 /**
047 * {@inheritDoc}
048 */
049 public int compare( String s1, String s2 )
050 {
051 // -------------------------------------------------------------------
052 // Handle some basis cases
053 // -------------------------------------------------------------------
054 if ( s1 == null )
055 {
056 return ( s2 == null ) ? 0 : -1;
057 }
058
059 if ( s2 == null )
060 {
061 return -1;
062 }
063
064 // Let's try to avoid a parse.
065 if ( s1.equals( s2 ) )
066 {
067 return 0;
068 }
069
070 // Parse the comparators now
071 synchronized ( normalizerParser )
072 {
073 AbstractSchemaDescription n1 = null;
074 AbstractSchemaDescription n2 = null;
075
076 try
077 {
078 n1 = normalizerParser.parse( s1 );
079 }
080 catch ( ParseException pe )
081 {
082 return -1;
083 }
084
085 try
086 {
087 n2 = normalizerParser.parse( s2 );
088 }
089 catch ( ParseException pe )
090 {
091 return -1;
092 }
093
094 // The OID is the only criterium for a comparison
095 return ( n1.getNumericOid().compareTo( n2.getNumericOid() ) );
096 }
097 }
098 }