Lucene example source code file (FieldNormModifier.java)

This example Lucene source code file (FieldNormModifier.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

directory, exception, fieldinvertstate, fieldinvertstate, fieldnormmodifier, fieldnormmodifier, file, io, ioexception, ioexception, similarity, similarity, string, term, termenum, util

The Lucene FieldNormModifier.java source code

package org.apache.lucene.index;

/**
 * Copyright 2006 The Apache Software Foundation
 *
 * 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.
 */

import java.io.IOException;
import java.io.File;
import java.util.Date;

import org.apache.lucene.search.Similarity;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import org.apache.lucene.util.StringHelper;

/**
 * Given a directory and a list of fields, updates the fieldNorms in place for every document.
 * 
 * If Similarity class is specified, uses its computeNorm method to set norms.
 * If -n command line argument is used, removed field norms, as if 
 * {@link org.apache.lucene.document.Field.Index}.NO_NORMS was used.
 *
 * <p>
 * NOTE: This will overwrite any length normalization or field/document boosts.
 * </p>
 *
 */
public class FieldNormModifier {

  /**
   * Command Line Execution method.
   *
   * <pre>
   * Usage: FieldNormModifier /path/index <package.SimilarityClassName | -n> field1 field2 ...
   * </pre>
   */
  public static void main(String[] args) throws IOException {
    if (args.length < 3) {
      System.err.println("Usage: FieldNormModifier <index>   [field2] ...");
      System.exit(1);
    }

    Similarity s = null;
    if (!args[1].equals("-n")) {
      try {
        s = Class.forName(args[1]).asSubclass(Similarity.class).newInstance();
      } catch (Exception e) {
        System.err.println("Couldn't instantiate similarity with empty constructor: " + args[1]);
        e.printStackTrace(System.err);
        System.exit(1);
      }
    }

    Directory d = FSDirectory.open(new File(args[0]));
    FieldNormModifier fnm = new FieldNormModifier(d, s);

    for (int i = 2; i < args.length; i++) {
      System.out.print("Updating field: " + args[i] + " " + (new Date()).toString() + " ... ");
      fnm.reSetNorms(args[i]);
      System.out.println(new Date().toString());
    }
    
    d.close();
  }
  
  
  private Directory dir;
  private Similarity sim;
  
  /**
   * Constructor for code that wishes to use this class programmatically
   * If Similarity is null, kill the field norms.
   *
   * @param d the Directory to modify
   * @param s the Similarity to use (can be null)
   */
  public FieldNormModifier(Directory d, Similarity s) {
    dir = d;
    sim = s;
  }

  /**
   * Resets the norms for the specified field.
   *
   * <p>
   * Opens a new IndexReader on the Directory given to this instance,
   * modifies the norms (either using the Similarity given to this instance, or by using fake norms,
   * and closes the IndexReader.
   * </p>
   *
   * @param field the field whose norms should be reset
   */
  public void reSetNorms(String field) throws IOException {
    String fieldName = StringHelper.intern(field);
    int[] termCounts = new int[0];
    
    IndexReader reader = null;
    TermEnum termEnum = null;
    TermDocs termDocs = null;
    try {
      reader = IndexReader.open(dir, true);
      termCounts = new int[reader.maxDoc()];
      try {
        termEnum = reader.terms(new Term(field));
        try {
          termDocs = reader.termDocs();
          do {
            Term term = termEnum.term();
            if (term != null && term.field().equals(fieldName)) {
              termDocs.seek(termEnum.term());
              while (termDocs.next()) {
                termCounts[termDocs.doc()] += termDocs.freq();
              }
            }
          } while (termEnum.next());
          
        } finally {
          if (null != termDocs) termDocs.close();
        }
      } finally {
        if (null != termEnum) termEnum.close();
      }
    } finally {
      if (null != reader) reader.close();
    }
    
    try {
      reader = IndexReader.open(dir, false); 
      final FieldInvertState invertState = new FieldInvertState();
      invertState.setBoost(1.0f);
      for (int d = 0; d < termCounts.length; d++) {
        if (! reader.isDeleted(d)) {
          if (sim == null)
            reader.setNorm(d, fieldName, Similarity.encodeNorm(1.0f));
          else {
            invertState.setLength(termCounts[d]);
            reader.setNorm(d, fieldName, sim.encodeNormValue(sim.computeNorm(fieldName, invertState)));
          }
        }
      }
      
    } finally {
      if (null != reader) reader.close();
    }
  }
  
}