/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.lucene.collation; import java.text.Collator; import org.apache.lucene.analysis.TokenStream; import org.apache.lucene.collation.tokenattributes.CollatedTermAttributeImpl; import org.apache.lucene.util.AttributeFactory; /** *
* Converts each token into its {@link java.text.CollationKey}, and then * encodes the bytes as an index term. *
** WARNING: Make sure you use exactly the same Collator at * index and query time -- CollationKeys are only comparable when produced by * the same Collator. Since {@link java.text.RuleBasedCollator}s are not * independently versioned, it is unsafe to search against stored * CollationKeys unless the following are exactly the same (best practice is * to store this information with the index and check that they remain the * same at query time): *
*
* The ICUCollationAttributeFactory
in the analysis-icu package
* uses ICU4J's Collator, which makes its
* version available, thus allowing collation to be versioned independently
* from the JVM. ICUCollationAttributeFactory is also significantly faster and
* generates significantly shorter keys than CollationAttributeFactory. See
* http://site.icu-project.org/charts/collation-icu4j-sun for key
* generation timing and key length comparisons between ICU4J and
* java.text.Collator over several languages.
*
* CollationKeys generated by java.text.Collators are not compatible * with those those generated by ICU Collators. Specifically, if you use * CollationAttributeFactory to generate index terms, do not use * ICUCollationAttributeFactory on the query side, or vice versa. *
*/ public class CollationAttributeFactory extends AttributeFactory.StaticImplementationAttributeFactory