org.apache.lucene.collation.CollationKeyAnalyzer Maven / Gradle / Ivy
/*
* 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 org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.core.KeywordTokenizer;
import org.apache.lucene.util.AttributeFactory;
import java.text.Collator;
/**
*
* Configures {@link KeywordTokenizer} with {@link CollationAttributeFactory}.
*
*
* Converts the token into its {@link java.text.CollationKey}, and then
* encodes the CollationKey directly to allow
* it to be stored 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):
*
*
* - JVM vendor
* - JVM version, including patch version
* -
* The language (and country and variant, if specified) of the Locale
* used when constructing the collator via
* {@link Collator#getInstance(java.util.Locale)}.
*
* -
* The collation strength used - see {@link Collator#setStrength(int)}
*
*
*
* The ICUCollationKeyAnalyzer in the analysis-icu package
* uses ICU4J's Collator, which makes
* its version available, thus allowing collation to be versioned
* independently from the JVM. ICUCollationKeyAnalyzer is also significantly
* faster and generates significantly shorter keys than CollationKeyAnalyzer.
* 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
* CollationKeyAnalyzer to generate index terms, do not use
* ICUCollationKeyAnalyzer on the query side, or vice versa.
*
*
* @since 3.1
*/
public final class CollationKeyAnalyzer extends Analyzer {
private final CollationAttributeFactory factory;
/**
* Create a new CollationKeyAnalyzer, using the specified collator.
*
* @param collator CollationKey generator
*/
public CollationKeyAnalyzer(Collator collator) {
this.factory = new CollationAttributeFactory(collator);
}
@Override
protected AttributeFactory attributeFactory(String fieldName) {
return factory;
}
@Override
protected TokenStreamComponents createComponents(String fieldName) {
KeywordTokenizer tokenizer = new KeywordTokenizer(factory, KeywordTokenizer.DEFAULT_BUFFER_SIZE);
return new TokenStreamComponents(tokenizer, tokenizer);
}
}