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 com.ibm.icu.text.Collator;
import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.KeywordTokenizer;
import org.apache.lucene.analysis.Tokenizer;
import org.apache.lucene.collation.CollationKeyAnalyzer; // javadocs
import java.io.Reader;
import java.io.IOException;
/**
* <p>
* Filters {@link KeywordTokenizer} with {@link ICUCollationKeyFilter}.
* <p>
* Converts the token into its {@link com.ibm.icu.text.CollationKey}, and
* then encodes the CollationKey with
* {@link org.apache.lucene.util.IndexableBinaryStringTools}, 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. {@link com.ibm.icu.text.RuleBasedCollator}s are
* independently versioned, so it is safe to search against stored
* CollationKeys if 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>
* Collator version - see {@link Collator#getVersion()}
* </li>
* <li>
* The collation strength used - see {@link Collator#setStrength(int)}
* </li>
* </ol>
* <p>
* CollationKeys generated by ICU Collators are not compatible with those
* generated by java.text.Collators. Specifically, if you use
* ICUCollationKeyAnalyzer to generate index terms, do not use
* {@link CollationKeyAnalyzer} on the query side, or vice versa.
* </p>
* <p>
* ICUCollationKeyAnalyzer is 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>
*/
public final class ICUCollationKeyAnalyzer extends Analyzer {
private Collator collator;
public ICUCollationKeyAnalyzer(Collator collator) {
this.collator = collator;
}
@Override
public TokenStream tokenStream(String fieldName, Reader reader) {
TokenStream result = new KeywordTokenizer(reader);
result = new ICUCollationKeyFilter(result, collator);
return result;
}
private class SavedStreams {
Tokenizer source;
TokenStream result;
}
@Override
public TokenStream reusableTokenStream(String fieldName, Reader reader)
throws IOException {
SavedStreams streams = (SavedStreams)getPreviousTokenStream();
if (streams == null) {
streams = new SavedStreams();
streams.source = new KeywordTokenizer(reader);
streams.result = new ICUCollationKeyFilter(streams.source, collator);
setPreviousTokenStream(streams);
} else {
streams.source.reset(reader);
}
return streams.result;
}
}