org.apache.lucene.analysis.opennlp.tools.NLPLemmatizerOp Maven / Gradle / Ivy
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* 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
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package org.apache.lucene.analysis.opennlp.tools;
import java.io.IOException;
import java.io.InputStream;
import opennlp.tools.lemmatizer.DictionaryLemmatizer;
import opennlp.tools.lemmatizer.LemmatizerME;
import opennlp.tools.lemmatizer.LemmatizerModel;
/**
* Supply OpenNLP Lemmatizer tools.
*
* Both a dictionary-based lemmatizer and a MaxEnt lemmatizer are supported.
* If both are configured, the dictionary-based lemmatizer is tried first,
* and then the MaxEnt lemmatizer is consulted for out-of-vocabulary tokens.
*
*
* The MaxEnt implementation requires binary models from OpenNLP project on SourceForge.
*
*/
public class NLPLemmatizerOp {
private final DictionaryLemmatizer dictionaryLemmatizer;
private final LemmatizerME lemmatizerME;
public NLPLemmatizerOp(InputStream dictionary, LemmatizerModel lemmatizerModel) throws IOException {
assert dictionary != null || lemmatizerModel != null : "At least one parameter must be non-null";
dictionaryLemmatizer = dictionary == null ? null : new DictionaryLemmatizer(dictionary);
lemmatizerME = lemmatizerModel == null ? null : new LemmatizerME(lemmatizerModel);
}
public String[] lemmatize(String[] words, String[] postags) {
String[] lemmas = null;
String[] maxEntLemmas = null;
if (dictionaryLemmatizer != null) {
lemmas = dictionaryLemmatizer.lemmatize(words, postags);
for (int i = 0; i < lemmas.length; ++i) {
if (lemmas[i].equals("O")) { // this word is not in the dictionary
if (lemmatizerME != null) { // fall back to the MaxEnt lemmatizer if it's enabled
if (maxEntLemmas == null) {
maxEntLemmas = lemmatizerME.lemmatize(words, postags);
}
if ("_".equals(maxEntLemmas[i])) {
lemmas[i] = words[i]; // put back the original word if no lemma is found
} else {
lemmas[i] = maxEntLemmas[i];
}
} else { // there is no MaxEnt lemmatizer
lemmas[i] = words[i]; // put back the original word if no lemma is found
}
}
}
} else { // there is only a MaxEnt lemmatizer
maxEntLemmas = lemmatizerME.lemmatize(words, postags);
for (int i = 0 ; i < maxEntLemmas.length ; ++i) {
if ("_".equals(maxEntLemmas[i])) {
maxEntLemmas[i] = words[i]; // put back the original word if no lemma is found
}
}
lemmas = maxEntLemmas;
}
return lemmas;
}
}