package org.apache.lucene.collation;
/*
* 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.
*/
import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.core.KeywordTokenizer;
import org.apache.lucene.util.IndexableBinaryStringTools; // javadoc @link
import org.apache.lucene.util.Version;
import java.text.Collator;
import java.io.Reader;
/**
* <p>
* Configures {@link KeywordTokenizer} with {@link CollationAttributeFactory}.
* </p>
* <p>
* Converts the token into its {@link java.text.CollationKey}, and then
* encodes the CollationKey either directly or with
* {@link IndexableBinaryStringTools} (see <a href="#version">below</a>), to allow
* it to be stored as an index term.
* </p>
* <p>
* <strong>WARNING:</strong> 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):
* </p>
* <ol>
* <li>JVM vendor</li>
* <li>JVM version, including patch version</li>
* <li>
* The language (and country and variant, if specified) of the Locale
* used when constructing the collator via
* {@link Collator#getInstance(java.util.Locale)}.
* </li>
* <li>
* The collation strength used - see {@link Collator#setStrength(int)}
* </li>
* </ol>
* <p>
* The <code>ICUCollationKeyAnalyzer</code> in the analysis-icu package
* uses ICU4J's Collator, which makes its
* 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 <a href="http://site.icu-project.org/charts/collation-icu4j-sun"
* >http://site.icu-project.org/charts/collation-icu4j-sun</a> for key
* generation timing and key length comparisons between ICU4J and
* java.text.Collator over several languages.
* </p>
* <p>
* 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.
* </p>
* <a name="version"/>
* <p>You must specify the required {@link Version}
* compatibility when creating CollationKeyAnalyzer:
* <ul>
* <li> As of 4.0, Collation Keys are directly encoded as bytes. Previous
* versions will encode the bytes with {@link IndexableBinaryStringTools}.
* </ul>
*/
public final class CollationKeyAnalyzer extends Analyzer {
private final Collator collator;
private final CollationAttributeFactory factory;
private final Version matchVersion;
/**
* Create a new CollationKeyAnalyzer, using the specified collator.
*
* @param matchVersion See <a href="#version">above</a>
* @param collator CollationKey generator
*/
public CollationKeyAnalyzer(Version matchVersion, Collator collator) {
this.matchVersion = matchVersion;
this.collator = collator;
this.factory = new CollationAttributeFactory(collator);
}
/**
* @deprecated Use {@link CollationKeyAnalyzer#CollationKeyAnalyzer(Version, Collator)}
* and specify a version instead. This ctor will be removed in Lucene 5.0
*/
@Deprecated
public CollationKeyAnalyzer(Collator collator) {
this(Version.LUCENE_3_1, collator);
}
@Override
protected TokenStreamComponents createComponents(String fieldName,
Reader reader) {
if (matchVersion.onOrAfter(Version.LUCENE_4_0)) {
KeywordTokenizer tokenizer = new KeywordTokenizer(factory, reader, KeywordTokenizer.DEFAULT_BUFFER_SIZE);
return new TokenStreamComponents(tokenizer, tokenizer);
} else {
KeywordTokenizer tokenizer = new KeywordTokenizer(reader);
return new TokenStreamComponents(tokenizer, new CollationKeyFilter(tokenizer, collator));
}
}
}