org.elasticsearch.index.analysis.CJKBigramFilterFactory Maven / Gradle / Ivy
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* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch 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.elasticsearch.index.analysis;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.cjk.CJKBigramFilter;
import org.elasticsearch.common.inject.Inject;
import org.elasticsearch.common.inject.assistedinject.Assisted;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.index.Index;
import org.elasticsearch.index.settings.IndexSettingsService;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;
/**
* Factory that creates a {@link CJKBigramFilter} to form bigrams of CJK terms
* that are generated from StandardTokenizer or ICUTokenizer.
*
* CJK types are set by these tokenizers, but you can also use flags to
* explicitly control which of the CJK scripts are turned into bigrams.
*
* By default, when a CJK character has no adjacent characters to form a bigram,
* it is output in unigram form. If you want to always output both unigrams and
* bigrams, set the outputUnigrams
flag. This can be used for a
* combined unigram+bigram approach.
*
* In all cases, all non-CJK input is passed thru unmodified.
*/
public final class CJKBigramFilterFactory extends AbstractTokenFilterFactory {
private final int flags;
private final boolean outputUnigrams;
@Inject
public CJKBigramFilterFactory(Index index, IndexSettingsService indexSettingsService, @Assisted String name, @Assisted Settings settings) {
super(index, indexSettingsService.getSettings(), name, settings);
outputUnigrams = settings.getAsBoolean("output_unigrams", false);
final String[] asArray = settings.getAsArray("ignored_scripts");
Set scripts = new HashSet<>(Arrays.asList("han", "hiragana", "katakana", "hangul"));
if (asArray != null) {
scripts.removeAll(Arrays.asList(asArray));
}
int flags = 0;
for (String script : scripts) {
if ("han".equals(script)) {
flags |= CJKBigramFilter.HAN;
} else if ("hiragana".equals(script)) {
flags |= CJKBigramFilter.HIRAGANA;
} else if ("katakana".equals(script)) {
flags |= CJKBigramFilter.KATAKANA;
} else if ("hangul".equals(script)) {
flags |= CJKBigramFilter.HANGUL;
}
}
this.flags = flags;
}
@Override
public TokenStream create(TokenStream tokenStream) {
return new CJKBigramFilter(tokenStream, flags, outputUnigrams);
}
}