Lucene example source code file (TermVectorAccessor.java)

This example Lucene source code file (TermVectorAccessor.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Lucene tags/keywords

arraylist, arraylist, io, ioexception, list, override, override, string, termenum, termvectoraccessor, termvectormapper, termvectormapper, termvectormapperdecorator, termvectormapperdecorator, termvectoroffsetinfo, util

The Lucene TermVectorAccessor.java source code

package org.apache.lucene.index;

import org.apache.lucene.util.StringHelper;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
/*
 *  Licensed 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.
 *
 */


/**
 * Transparent access to the vector space model,
 * either via TermFreqVector or by resolving it from the inverted index.
 * <p/>
 * Resolving a term vector from a large index can be a time consuming process.
 * <p/>
 * Warning! This class is not thread safe!
 */
public class TermVectorAccessor {

  public TermVectorAccessor() {
  }

  /**
   * Instance reused to save garbage collector some time
   */
  private TermVectorMapperDecorator decoratedMapper = new TermVectorMapperDecorator();


  /**
   * Visits the TermVectorMapper and populates it with terms available for a given document,
   * either via a vector created at index time or by resolving them from the inverted index.
   *
   * @param indexReader    Index source
   * @param documentNumber Source document to access
   * @param fieldName      Field to resolve
   * @param mapper         Mapper to be mapped with data
   * @throws IOException
   */
  public void accept(IndexReader indexReader, int documentNumber, String fieldName, TermVectorMapper mapper) throws IOException {

    fieldName = StringHelper.intern(fieldName);

    decoratedMapper.decorated = mapper;
    decoratedMapper.termVectorStored = false;

    indexReader.getTermFreqVector(documentNumber, fieldName, decoratedMapper);

    if (!decoratedMapper.termVectorStored) {
      mapper.setDocumentNumber(documentNumber);
      build(indexReader, fieldName, mapper, documentNumber);
    }
  }

  /** Instance reused to save garbage collector some time */
  private List<String> tokens;

  /** Instance reused to save garbage collector some time */
  private List<int[]> positions;

  /** Instance reused to save garbage collector some time */
  private List<Integer> frequencies;


  /**
   * Populates the mapper with terms available for the given field in a document
   * by resolving the inverted index.
   *
   * @param indexReader
   * @param field interned field name
   * @param mapper
   * @param documentNumber
   * @throws IOException
   */
  private void build(IndexReader indexReader, String field, TermVectorMapper mapper, int documentNumber) throws IOException {

    if (tokens == null) {
      tokens = new ArrayList<String>(500);
      positions = new ArrayList<int[]>(500);
      frequencies = new ArrayList<Integer>(500);
    } else {
      tokens.clear();
      frequencies.clear();
      positions.clear();
    }

    TermEnum termEnum = indexReader.terms(new Term(field, ""));
    if (termEnum.term() != null) {
      while (termEnum.term().field() == field) {
        TermPositions termPositions = indexReader.termPositions(termEnum.term());
        if (termPositions.skipTo(documentNumber)) {
  
          frequencies.add(Integer.valueOf(termPositions.freq()));
          tokens.add(termEnum.term().text());
  
  
          if (!mapper.isIgnoringPositions()) {
            int[] positions = new int[termPositions.freq()];
            for (int i = 0; i < positions.length; i++) {
              positions[i] = termPositions.nextPosition();
            }
            this.positions.add(positions);
          } else {
            positions.add(null);
          }
        }
        termPositions.close();
        if (!termEnum.next()) {
          break;
        }
      }
      mapper.setDocumentNumber(documentNumber);
      mapper.setExpectations(field, tokens.size(), false, !mapper.isIgnoringPositions());
      for (int i = 0; i < tokens.size(); i++) {
        mapper.map(tokens.get(i), frequencies.get(i).intValue(), (TermVectorOffsetInfo[]) null, positions.get(i));
      }
    }
    termEnum.close();


  }


  private static class TermVectorMapperDecorator extends TermVectorMapper {

    private TermVectorMapper decorated;

    @Override
    public boolean isIgnoringPositions() {
      return decorated.isIgnoringPositions();
    }

    @Override
    public boolean isIgnoringOffsets() {
      return decorated.isIgnoringOffsets();
    }

    private boolean termVectorStored = false;

    @Override
    public void setExpectations(String field, int numTerms, boolean storeOffsets, boolean storePositions) {
      decorated.setExpectations(field, numTerms, storeOffsets, storePositions);
      termVectorStored = true;
    }

    @Override
    public void map(String term, int frequency, TermVectorOffsetInfo[] offsets, int[] positions) {
      decorated.map(term, frequency, offsets, positions);
    }

    @Override
    public void setDocumentNumber(int documentNumber) {
      decorated.setDocumentNumber(documentNumber);
    }
  }

}