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Lucene example source code file (ScoreCachingWrappingScorer.java)

This example Lucene source code file (ScoreCachingWrappingScorer.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

io, ioexception, ioexception, override, override, scorecachingwrappingscorer, scorecachingwrappingscorer, scorer, scorer, similarity

The Lucene ScoreCachingWrappingScorer.java source code

package org.apache.lucene.search;

/**
 * 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 java.io.IOException;

/**
 * A {@link Scorer} which wraps another scorer and caches the score of the
 * current document. Successive calls to {@link #score()} will return the same
 * result and will not invoke the wrapped Scorer's score() method, unless the
 * current document has changed.<br>
 * This class might be useful due to the changes done to the {@link Collector}
 * interface, in which the score is not computed for a document by default, only
 * if the collector requests it. Some collectors may need to use the score in
 * several places, however all they have in hand is a {@link Scorer} object, and
 * might end up computing the score of a document more than once.
 */
public class ScoreCachingWrappingScorer extends Scorer {

  private final Scorer scorer;
  private int curDoc = -1;
  private float curScore;
  
  /** Creates a new instance by wrapping the given scorer. */
  public ScoreCachingWrappingScorer(Scorer scorer) {
    super(scorer.getSimilarity(), scorer.weight);
    this.scorer = scorer;
  }

  @Override
  protected boolean score(Collector collector, int max, int firstDocID) throws IOException {
    return scorer.score(collector, max, firstDocID);
  }

  @Override
  public Similarity getSimilarity() {
    return scorer.getSimilarity();
  }
  
  @Override
  public float score() throws IOException {
    int doc = scorer.docID();
    if (doc != curDoc) {
      curScore = scorer.score();
      curDoc = doc;
    }
    
    return curScore;
  }

  @Override
  public int docID() {
    return scorer.docID();
  }

  @Override
  public int nextDoc() throws IOException {
    return scorer.nextDoc();
  }
  
  @Override
  public void score(Collector collector) throws IOException {
    scorer.score(collector);
  }
  
  @Override
  public int advance(int target) throws IOException {
    return scorer.advance(target);
  }
  
}

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