uimaj-2.2.0-incubating/uimaj-examples/src/main/opennlp_wrappers/src/org/apache/uima/examples/opennlp/annotator/POSTagger.java

/*
 * 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.
 */

package org.apache.uima.examples.opennlp.annotator;

import java.util.ArrayList;
import java.util.List;

import opennlp.tools.lang.english.PosTagger;
import opennlp.tools.ngram.Dictionary;

import org.apache.uima.UimaContext;
import org.apache.uima.analysis_component.JCasAnnotator_ImplBase;
import org.apache.uima.analysis_engine.AnalysisEngineProcessException;
import org.apache.uima.cas.FSIterator;
import org.apache.uima.cas.text.AnnotationIndex;
import org.apache.uima.examples.opennlp.Sentence;
import org.apache.uima.examples.opennlp.Token;
import org.apache.uima.jcas.JCas;
import org.apache.uima.resource.ResourceInitializationException;

/**
 * UIMA Analysis Engine that invokes the OpenNLP POS tagger. The OpenNLP POS tagger generates a
 * PennTreeBank style POS tags. This annotator assumes that sentences and tokens have already been
 * annotated in the CAS with Sentence and Token annotations, respectively. We iterate over
 * sentences, then iterate over tokens in the current sentece to accumlate a list of words, then
 * invoke the OpenNLP POS tagger on the list of words. For each Token we then update the posTag
 * field with the POS tag. The model file for the OpenNLP POS tagger is specified as a parameter
 * (MODEL_FILE_PARAM).
 * 
 */
public class POSTagger extends JCasAnnotator_ImplBase {

  public static final String MODEL_FILE_PARAM = "ModelFile";

  private PosTagger tagger;

  /**
   * Initialize the Annotator.
   * 
   * @see JCasAnnotator_ImplBase#initialize(UimaContext)
   */
  public void initialize(UimaContext aContext) throws ResourceInitializationException {
    super.initialize(aContext);

    try {
      // Get configuration parameter values
      String modelFile = (String) aContext.getConfigParameterValue(MODEL_FILE_PARAM);
      tagger = new PosTagger(modelFile, (Dictionary) null);
    } catch (Exception e) {
      throw new ResourceInitializationException(e);
    }
  }

  /**
   * Process a CAS.
   * 
   * @see JCasAnnotator_ImplBase#process(JCas)
   */
  public void process(JCas aJCas) throws AnalysisEngineProcessException {

    ArrayList tokenList = new ArrayList();
    ArrayList wordList = new ArrayList();

    AnnotationIndex sentenceIndex = aJCas.getAnnotationIndex(Sentence.type);
    AnnotationIndex tokenIndex = aJCas.getAnnotationIndex(Token.type);

    // iterate over Sentences
    FSIterator sentenceIterator = sentenceIndex.iterator();
    while (sentenceIterator.hasNext()) {
      Sentence sentence = (Sentence) sentenceIterator.next();

      tokenList.clear();
      wordList.clear();

      // iterate over Tokens
      FSIterator tokenIterator = tokenIndex.subiterator(sentence);
      while (tokenIterator.hasNext()) {
        Token token = (Token) tokenIterator.next();

        tokenList.add(token);
        wordList.add(token.getCoveredText());
      }

      List wordTagList = tagger.tag(wordList);

      try {
        for (int i = 0; i < tokenList.size(); i++) {
          Token token = (Token) tokenList.get(i);
          String posTag = (String) wordTagList.get(i);
          token.setPosTag(posTag);
        }
      } catch (IndexOutOfBoundsException e) {
        System.err.println("POS tagger error - list of tags shorter than list of words");
      }
    }
  }

}