// original code from Apache Solr - ported to work with Lucene 3.x and reformatted to Search coding style
/**
* 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.analysis;
import java.io.File;
import java.io.IOException;
import java.util.List;
import java.util.Map;
import org.apache.lucene.analysis.CharArraySet;
import org.apache.lucene.analysis.TokenFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.tokenattributes.TermAttribute;
import org.apache.solr.common.ResourceLoader;
import org.apache.solr.common.util.StrUtils;
import org.apache.solr.util.plugin.ResourceLoaderAware;
import org.tartarus.snowball.SnowballProgram;
/**
* Factory for SnowballFilters, with configurable language
* <p/>
* Browsing the code, SnowballFilter uses reflection to adapt to Lucene... don't
* use this if you are concerned about speed. Use EnglishPorterFilterFactory.
*
* @version $Id: SnowballPorterFilterFactory.java 804726 2009-08-16 17:28:58Z yonik $
*/
public class SnowballPorterFilterFactory extends BaseTokenFilterFactory implements ResourceLoaderAware {
public static final String PROTECTED_TOKENS = "protected";
private String language = "English";
private Class stemClass;
public void inform(ResourceLoader loader) {
String wordFiles = args.get( PROTECTED_TOKENS );
if ( wordFiles != null ) {
try {
File protectedWordFiles = new File( wordFiles );
if ( protectedWordFiles.exists() ) {
List<String> wlist = loader.getLines( wordFiles );
//This cast is safe in Lucene
protectedWords = new CharArraySet(
wlist, false
);//No need to go through StopFilter as before, since it just uses a List internally
}
else {
List<String> files = StrUtils.splitFileNames( wordFiles );
for ( String file : files ) {
List<String> wlist = loader.getLines( file.trim() );
if ( protectedWords == null ) {
protectedWords = new CharArraySet( wlist, false );
}
else {
protectedWords.addAll( wlist );
}
}
}
}
catch ( IOException e ) {
throw new RuntimeException( e );
}
}
}
private CharArraySet protectedWords = null;
@Override
public void init(Map<String, String> args) {
super.init( args );
final String cfgLanguage = args.get( "language" );
if ( cfgLanguage != null ) {
language = cfgLanguage;
}
try {
stemClass = Class.forName( "org.tartarus.snowball.ext." + language + "Stemmer" );
}
catch ( ClassNotFoundException e ) {
throw new RuntimeException( "Can't find class for stemmer language " + language, e );
}
}
public SnowballPorterFilter create(TokenStream input) {
SnowballProgram program;
try {
program = ( SnowballProgram ) stemClass.newInstance();
}
catch ( Exception e ) {
throw new RuntimeException(
"Error instantiating stemmer for language " + language + "from class " + stemClass, e
);
}
return new SnowballPorterFilter( input, program, protectedWords );
}
}
class SnowballPorterFilter extends TokenFilter {
private final CharArraySet protWords;
private final SnowballProgram stemmer;
private final TermAttribute termAtt;
public SnowballPorterFilter(TokenStream source, SnowballProgram stemmer, CharArraySet protWords) {
super( source );
this.protWords = protWords;
this.stemmer = stemmer;
this.termAtt = ( TermAttribute ) addAttribute( TermAttribute.class );
}
@Override
public boolean incrementToken() throws IOException {
if ( !input.incrementToken() ) {
return false;
}
char[] termBuffer = termAtt.termBuffer();
int len = termAtt.termLength();
// if protected, don't stem. use this to avoid stemming collisions.
if ( protWords != null && protWords.contains( termBuffer, 0, len ) ) {
return true;
}
stemmer.setCurrent( new String( termBuffer, 0, len ) );//ugh, wish the Stemmer took a char array
stemmer.stem();
String newstr = stemmer.getCurrent();
termAtt.setTermBuffer( newstr.toCharArray(), 0, newstr.length() );
return true;
}
}