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.TokenStream;
import org.apache.lucene.collation.tokenattributes.ICUCollatedTermAttributeImpl;
import org.apache.lucene.util.AttributeFactory;
import com.ibm.icu.text.Collator;
/**
* <p>
* Converts each token into its {@link com.ibm.icu.text.CollationKey}, and
* then encodes bytes 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
* ICUCollationAttributeFactory to generate index terms, do not use
* {@link CollationAttributeFactory} on the query side, or vice versa.
* </p>
* <p>
* ICUCollationAttributeFactory is significantly faster and generates significantly
* shorter keys than CollationAttributeFactory. 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 class ICUCollationAttributeFactory extends AttributeFactory.StaticImplementationAttributeFactory<ICUCollatedTermAttributeImpl> {
private final Collator collator;
/**
* Create an ICUCollationAttributeFactory, using
* {@link TokenStream#DEFAULT_TOKEN_ATTRIBUTE_FACTORY} as the
* factory for all other attributes.
* @param collator CollationKey generator
*/
public ICUCollationAttributeFactory(Collator collator) {
this(TokenStream.DEFAULT_TOKEN_ATTRIBUTE_FACTORY, collator);
}
/**
* Create an ICUCollationAttributeFactory, using the supplied Attribute
* Factory as the factory for all other attributes.
* @param delegate Attribute Factory
* @param collator CollationKey generator
*/
public ICUCollationAttributeFactory(AttributeFactory delegate, Collator collator) {
super(delegate, ICUCollatedTermAttributeImpl.class);
this.collator = collator;
}
@Override
public ICUCollatedTermAttributeImpl createInstance() {
return new ICUCollatedTermAttributeImpl(collator);
}
}