package ivory.core.tokenize;
import ivory.core.Constants;
import java.io.IOException;
import java.io.StringReader;
import java.util.Set;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.log4j.Level;
import org.apache.log4j.Logger;
import org.apache.lucene.analysis.CharArraySet;
import org.apache.lucene.analysis.LowerCaseFilter;
import org.apache.lucene.analysis.StopFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.ar.ArabicAnalyzer;
import org.apache.lucene.analysis.ar.ArabicNormalizationFilter;
import org.apache.lucene.analysis.ar.ArabicStemFilter;
import org.apache.lucene.analysis.standard.StandardTokenizer;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.util.Version;
public class LuceneArabicAnalyzer extends ivory.core.tokenize.Tokenizer {
private static final Logger LOG = Logger.getLogger(LuceneArabicAnalyzer.class);
static{
LOG.setLevel(Level.WARN);
}
private boolean isStemming;
private org.apache.lucene.analysis.Tokenizer tokenizer;
private Set<String> stopwords;
private Set<String> stemmedStopwords;
@Override
public void configure(Configuration conf) {
configure(conf, null);
}
@Override
public void configure(Configuration conf, FileSystem fs) {
// read stopwords from file (stopwords will be empty set if file does not exist or is empty)
String stopwordsFile = conf.get(Constants.StopwordList);
stopwords = readInput(fs, stopwordsFile);
String stemmedStopwordsFile = conf.get(Constants.StemmedStopwordList);
stemmedStopwords = readInput(fs, stemmedStopwordsFile);
isStopwordRemoval = !stopwords.isEmpty();
isStemming = conf.getBoolean(Constants.Stemming, true);
LOG.warn("Stemming is " + isStemming + "; Stopword removal is " + isStopwordRemoval +"; number of stopwords: " + stopwords.size() +"; stemmed: " + stemmedStopwords.size());
}
@Override
public String[] processContent(String text) {
tokenizer = new StandardTokenizer(Version.LUCENE_35, new StringReader(text));
TokenStream tokenStream = new LowerCaseFilter(Version.LUCENE_35, tokenizer);
if (isStopwordRemoval) {
tokenStream = new StopFilter( Version.LUCENE_35, tokenStream, (CharArraySet) ArabicAnalyzer.getDefaultStopSet());
}
tokenStream = new ArabicNormalizationFilter(tokenStream);
if (isStemming) {
tokenStream = new ArabicStemFilter(tokenStream);
}
CharTermAttribute termAtt = tokenStream.getAttribute(CharTermAttribute.class);
tokenStream.clearAttributes();
String tokenized = "";
try {
while (tokenStream.incrementToken()) {
String token = termAtt.toString();
if ( vocab != null && vocab.get(token) <= 0) {
continue;
}
tokenized += ( token + " " );
}
} catch (IOException e) {
e.printStackTrace();
}
return tokenized.trim().split("\\s+");
}
@Override
public boolean isStopWord(String token) {
return stopwords.contains(token) || delims.contains(token) || token.length()==1;
}
@Override
public String stem(String token) {
tokenizer = new StandardTokenizer(Version.LUCENE_35, new StringReader(token));
TokenStream tokenStream = new LowerCaseFilter(Version.LUCENE_35, tokenizer);
tokenStream = new ArabicNormalizationFilter(tokenStream);
tokenStream = new ArabicStemFilter(tokenStream);
CharTermAttribute termAtt = tokenStream.getAttribute(CharTermAttribute.class);
tokenStream.clearAttributes();
try {
while (tokenStream.incrementToken()) {
return termAtt.toString();
}
}catch (IOException e) {
e.printStackTrace();
}
return token;
}
@Override
public boolean isStemmedStopWord(String token) {
return stemmedStopwords.contains(token) || delims.contains(token) || token.length()==1;
}
}