/**
* 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.solr.highlight;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;
import org.apache.lucene.analysis.tokenattributes.PositionIncrementAttribute;
import org.apache.lucene.search.highlight.Fragmenter;
import org.apache.lucene.search.highlight.NullFragmenter;
import org.apache.lucene.search.highlight.SimpleFragmenter;
import org.apache.solr.common.params.DefaultSolrParams;
import org.apache.solr.common.params.HighlightParams;
import org.apache.solr.common.params.SolrParams;
public class GapFragmenter extends HighlightingPluginBase implements SolrFragmenter
{
public Fragmenter getFragmenter(String fieldName, SolrParams params )
{
numRequests++;
if( defaults != null ) {
params = new DefaultSolrParams( params, defaults );
}
int fragsize = params.getFieldInt( fieldName, HighlightParams.FRAGSIZE, 100 );
return (fragsize <= 0) ? new NullFragmenter() : new LuceneGapFragmenter(fragsize);
}
///////////////////////////////////////////////////////////////////////
//////////////////////// SolrInfoMBeans methods ///////////////////////
///////////////////////////////////////////////////////////////////////
@Override
public String getDescription() {
return "GapFragmenter";
}
@Override
public String getVersion() {
return "$Revision: 1065312 $";
}
@Override
public String getSourceId() {
return "$Id: GapFragmenter.java 1065312 2011-01-30 16:08:25Z rmuir $";
}
@Override
public String getSource() {
return "$URL: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene_solr_3_5/solr/core/src/java/org/apache/solr/highlight/GapFragmenter.java $";
}
}
/**
* A simple modification of SimpleFragmenter which additionally creates new
* fragments when an unusually-large position increment is encountered
* (this behaves much better in the presence of multi-valued fields).
*/
class LuceneGapFragmenter extends SimpleFragmenter {
/**
* When a gap in term positions is observed that is at least this big, treat
* the gap as a fragment delimiter.
*/
public static final int INCREMENT_THRESHOLD = 50;
protected int fragOffset = 0;
private OffsetAttribute offsetAtt;
private PositionIncrementAttribute posIncAtt;
public LuceneGapFragmenter() {
}
public LuceneGapFragmenter(int fragsize) {
super(fragsize);
}
/* (non-Javadoc)
* @see org.apache.lucene.search.highlight.TextFragmenter#start(java.lang.String)
*/
@Override
public void start(String originalText, TokenStream tokenStream) {
offsetAtt = tokenStream.getAttribute(OffsetAttribute.class);
posIncAtt = tokenStream.getAttribute(PositionIncrementAttribute.class);
fragOffset = 0;
}
/* (non-Javadoc)
* @see org.apache.lucene.search.highlight.TextFragmenter#isNewFragment(org.apache.lucene.analysis.Token)
*/
@Override
public boolean isNewFragment() {
int endOffset = offsetAtt.endOffset();
boolean isNewFrag =
endOffset >= fragOffset + getFragmentSize() ||
posIncAtt.getPositionIncrement() > INCREMENT_THRESHOLD;
if(isNewFrag) {
fragOffset = endOffset;
}
return isNewFrag;
}
}