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Lucene example source code file (BaseFragmentsBuilder.java)

This example Lucene source code file (BaseFragmentsBuilder.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

document, encoder, field, fieldfraglist, indexreader, indexreader, io, ioexception, ioexception, null_encoder, string, string, stringbuilder, stringbuilder, util, weightedfraginfo

The Lucene BaseFragmentsBuilder.java source code

package org.apache.lucene.search.vectorhighlight;

/**
 * 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;
import java.util.ArrayList;
import java.util.List;

import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.document.MapFieldSelector;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.highlight.DefaultEncoder;
import org.apache.lucene.search.highlight.Encoder;
import org.apache.lucene.search.vectorhighlight.FieldFragList.WeightedFragInfo;
import org.apache.lucene.search.vectorhighlight.FieldFragList.WeightedFragInfo.SubInfo;
import org.apache.lucene.search.vectorhighlight.FieldPhraseList.WeightedPhraseInfo.Toffs;

public abstract class BaseFragmentsBuilder implements FragmentsBuilder {

  protected String[] preTags, postTags;
  public static final String[] COLORED_PRE_TAGS = {
    "<b style=\"background:yellow\">", "", "",
    "<b style=\"background:magenta\">", "", "",
    "<b style=\"background:wheat\">", "", "",
    "<b style=\"background:deepskyblue\">", "", "",
    "<b style=\"background:peachpuff\">", "", "",
    "<b style=\"background:palegoldenrod\">", "", "",
    "<b style=\"background:turquoise\">", ""
  };
  public static final String[] COLORED_POST_TAGS = { "</b>" };
  private char multiValuedSeparator = ' ';
  
  protected BaseFragmentsBuilder(){
    this( new String[]{ "<b>" }, new String[]{ "" } );
  }
  
  protected BaseFragmentsBuilder( String[] preTags, String[] postTags ){
    this.preTags = preTags;
    this.postTags = postTags;
  }
  
  static Object checkTagsArgument( Object tags ){
    if( tags instanceof String ) return tags;
    else if( tags instanceof String[] ) return tags;
    throw new IllegalArgumentException( "type of preTags/postTags must be a String or String[]" );
  }
  
  public abstract List<WeightedFragInfo> getWeightedFragInfoList( List src );

  private static final Encoder NULL_ENCODER = new DefaultEncoder();
  
  public String createFragment( IndexReader reader, int docId,
      String fieldName, FieldFragList fieldFragList ) throws IOException {
    return createFragment( reader, docId, fieldName, fieldFragList,
        preTags, postTags, NULL_ENCODER );
  }

  public String[] createFragments( IndexReader reader, int docId,
      String fieldName, FieldFragList fieldFragList, int maxNumFragments )
      throws IOException {
    return createFragments( reader, docId, fieldName, fieldFragList, maxNumFragments,
        preTags, postTags, NULL_ENCODER );
  }
  
  public String createFragment( IndexReader reader, int docId,
      String fieldName, FieldFragList fieldFragList, String[] preTags, String[] postTags,
      Encoder encoder ) throws IOException {
    String[] fragments = createFragments( reader, docId, fieldName, fieldFragList, 1,
        preTags, postTags, encoder );
    if( fragments == null || fragments.length == 0 ) return null;
    return fragments[0];
  }

  public String[] createFragments( IndexReader reader, int docId,
      String fieldName, FieldFragList fieldFragList, int maxNumFragments,
      String[] preTags, String[] postTags, Encoder encoder ) throws IOException {
    if( maxNumFragments < 0 )
      throw new IllegalArgumentException( "maxNumFragments(" + maxNumFragments + ") must be positive number." );

    List<WeightedFragInfo> fragInfos = getWeightedFragInfoList( fieldFragList.getFragInfos() );
    
    List<String> fragments = new ArrayList( maxNumFragments );
    Field[] values = getFields( reader, docId, fieldName );
    if( values.length == 0 ) return null;
    StringBuilder buffer = new StringBuilder();
    int[] nextValueIndex = { 0 };
    for( int n = 0; n < maxNumFragments && n < fragInfos.size(); n++ ){
      WeightedFragInfo fragInfo = fragInfos.get( n );
      fragments.add( makeFragment( buffer, nextValueIndex, values, fragInfo, preTags, postTags, encoder ) );
    }
    return fragments.toArray( new String[fragments.size()] );
  }
  
  @Deprecated
  protected String[] getFieldValues( IndexReader reader, int docId, String fieldName) throws IOException {
    Document doc = reader.document( docId, new MapFieldSelector( new String[]{ fieldName } ) );
    return doc.getValues( fieldName ); // according to Document class javadoc, this never returns null
  }
  
  protected Field[] getFields( IndexReader reader, int docId, String fieldName) throws IOException {
    // according to javadoc, doc.getFields(fieldName) cannot be used with lazy loaded field???
    Document doc = reader.document( docId, new MapFieldSelector( new String[]{ fieldName } ) );
    return doc.getFields( fieldName ); // according to Document class javadoc, this never returns null
  }

  @Deprecated
  protected String makeFragment( StringBuilder buffer, int[] index, String[] values, WeightedFragInfo fragInfo ){
    final int s = fragInfo.startOffset;
    return makeFragment( fragInfo, getFragmentSource( buffer, index, values, s, fragInfo.endOffset ), s,
        preTags, postTags, NULL_ENCODER );
  }

  protected String makeFragment( StringBuilder buffer, int[] index, Field[] values, WeightedFragInfo fragInfo,
      String[] preTags, String[] postTags, Encoder encoder ){
    final int s = fragInfo.startOffset;
    return makeFragment( fragInfo, getFragmentSource( buffer, index, values, s, fragInfo.endOffset ), s,
        preTags, postTags, encoder );
  }
  
  private String makeFragment( WeightedFragInfo fragInfo, String src, int s,
      String[] preTags, String[] postTags, Encoder encoder ){
    StringBuilder fragment = new StringBuilder();
    int srcIndex = 0;
    for( SubInfo subInfo : fragInfo.subInfos ){
      for( Toffs to : subInfo.termsOffsets ){
        fragment
          .append( encoder.encodeText( src.substring( srcIndex, to.startOffset - s ) ) )
          .append( getPreTag( preTags, subInfo.seqnum ) )
          .append( encoder.encodeText( src.substring( to.startOffset - s, to.endOffset - s ) ) )
          .append( getPostTag( postTags, subInfo.seqnum ) );
        srcIndex = to.endOffset - s;
      }
    }
    fragment.append( encoder.encodeText( src.substring( srcIndex ) ) );
    return fragment.toString();
  }
  
  @Deprecated
  protected String getFragmentSource( StringBuilder buffer, int[] index, String[] values,
      int startOffset, int endOffset ){
    while( buffer.length() < endOffset && index[0] < values.length ){
      buffer.append( values[index[0]] );
      buffer.append( multiValuedSeparator );
      index[0]++;
    }
    int eo = buffer.length() < endOffset ? buffer.length() : endOffset;
    return buffer.substring( startOffset, eo );
  }

  protected String getFragmentSource( StringBuilder buffer, int[] index, Field[] values,
      int startOffset, int endOffset ){
    while( buffer.length() < endOffset && index[0] < values.length ){
      buffer.append( values[index[0]].stringValue() );
      if( values[index[0]].isTokenized() )
        buffer.append( multiValuedSeparator );
      index[0]++;
    }
    int eo = buffer.length() < endOffset ? buffer.length() : endOffset;
    return buffer.substring( startOffset, eo );
  }
  
  public void setMultiValuedSeparator( char separator ){
    multiValuedSeparator = separator;
  }
  
  public char getMultiValuedSeparator(){
    return multiValuedSeparator;
  }

  protected String getPreTag( int num ){
    return getPreTag( preTags, num );
  }
  
  protected String getPostTag( int num ){
    return getPostTag( postTags, num );
  }
  
  protected String getPreTag( String[] preTags, int num ){
    int n = num % preTags.length;
    return preTags[n];
  }
  
  protected String getPostTag( String[] postTags, int num ){
    int n = num % postTags.length;
    return postTags[n];
  }
}

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