--- /dev/null
+package org.apache.lucene.analysis.ar;
+
+/**
+ * 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.File;
+import java.io.IOException;
+import java.io.Reader;
+import java.util.Hashtable;
+import java.util.Set;
+
+import org.apache.lucene.analysis.Analyzer;
+import org.apache.lucene.analysis.LowerCaseFilter;
+import org.apache.lucene.analysis.CharArraySet;
+import org.apache.lucene.analysis.KeywordMarkerFilter;
+import org.apache.lucene.analysis.StopFilter;
+import org.apache.lucene.analysis.StopwordAnalyzerBase;
+import org.apache.lucene.analysis.TokenStream;
+import org.apache.lucene.analysis.Tokenizer;
+import org.apache.lucene.analysis.WordlistLoader;
+import org.apache.lucene.analysis.standard.StandardTokenizer;
+import org.apache.lucene.util.IOUtils;
+import org.apache.lucene.util.Version;
+
+/**
+ * {@link Analyzer} for Arabic.
+ * <p>
+ * This analyzer implements light-stemming as specified by:
+ * <i>
+ * Light Stemming for Arabic Information Retrieval
+ * </i>
+ * http://www.mtholyoke.edu/~lballest/Pubs/arab_stem05.pdf
+ * <p>
+ * The analysis package contains three primary components:
+ * <ul>
+ * <li>{@link ArabicNormalizationFilter}: Arabic orthographic normalization.
+ * <li>{@link ArabicStemFilter}: Arabic light stemming
+ * <li>Arabic stop words file: a set of default Arabic stop words.
+ * </ul>
+ *
+ */
+public final class ArabicAnalyzer extends StopwordAnalyzerBase {
+
+ /**
+ * File containing default Arabic stopwords.
+ *
+ * Default stopword list is from http://members.unine.ch/jacques.savoy/clef/index.html
+ * The stopword list is BSD-Licensed.
+ */
+ public final static String DEFAULT_STOPWORD_FILE = "stopwords.txt";
+
+ /**
+ * The comment character in the stopwords file. All lines prefixed with this will be ignored
+ * @deprecated use {@link WordlistLoader#getWordSet(Reader, String, Version)} directly
+ */
+ // TODO make this private
+ @Deprecated
+ public static final String STOPWORDS_COMMENT = "#";
+
+ /**
+ * Returns an unmodifiable instance of the default stop-words set.
+ * @return an unmodifiable instance of the default stop-words set.
+ */
+ public static Set<?> getDefaultStopSet(){
+ return DefaultSetHolder.DEFAULT_STOP_SET;
+ }
+
+ /**
+ * Atomically loads the DEFAULT_STOP_SET in a lazy fashion once the outer class
+ * accesses the static final set the first time.;
+ */
+ private static class DefaultSetHolder {
+ static final Set<?> DEFAULT_STOP_SET;
+
+ static {
+ try {
+ DEFAULT_STOP_SET = loadStopwordSet(false, ArabicAnalyzer.class, DEFAULT_STOPWORD_FILE, STOPWORDS_COMMENT);
+ } catch (IOException ex) {
+ // default set should always be present as it is part of the
+ // distribution (JAR)
+ throw new RuntimeException("Unable to load default stopword set");
+ }
+ }
+ }
+
+ private final Set<?> stemExclusionSet;
+
+ /**
+ * Builds an analyzer with the default stop words: {@link #DEFAULT_STOPWORD_FILE}.
+ */
+ public ArabicAnalyzer(Version matchVersion) {
+ this(matchVersion, DefaultSetHolder.DEFAULT_STOP_SET);
+ }
+
+ /**
+ * Builds an analyzer with the given stop words
+ *
+ * @param matchVersion
+ * lucene compatibility version
+ * @param stopwords
+ * a stopword set
+ */
+ public ArabicAnalyzer(Version matchVersion, Set<?> stopwords){
+ this(matchVersion, stopwords, CharArraySet.EMPTY_SET);
+ }
+
+ /**
+ * Builds an analyzer with the given stop word. If a none-empty stem exclusion set is
+ * provided this analyzer will add a {@link KeywordMarkerFilter} before
+ * {@link ArabicStemFilter}.
+ *
+ * @param matchVersion
+ * lucene compatibility version
+ * @param stopwords
+ * a stopword set
+ * @param stemExclusionSet
+ * a set of terms not to be stemmed
+ */
+ public ArabicAnalyzer(Version matchVersion, Set<?> stopwords, Set<?> stemExclusionSet){
+ super(matchVersion, stopwords);
+ this.stemExclusionSet = CharArraySet.unmodifiableSet(CharArraySet.copy(
+ matchVersion, stemExclusionSet));
+ }
+
+ /**
+ * Builds an analyzer with the given stop words.
+ * @deprecated use {@link #ArabicAnalyzer(Version, Set)} instead
+ */
+ @Deprecated
+ public ArabicAnalyzer( Version matchVersion, String... stopwords ) {
+ this(matchVersion, StopFilter.makeStopSet(matchVersion, stopwords ));
+ }
+
+ /**
+ * Builds an analyzer with the given stop words.
+ * @deprecated use {@link #ArabicAnalyzer(Version, Set)} instead
+ */
+ @Deprecated
+ public ArabicAnalyzer( Version matchVersion, Hashtable<?,?> stopwords ) {
+ this(matchVersion, stopwords.keySet());
+ }
+
+ /**
+ * Builds an analyzer with the given stop words. Lines can be commented out using {@link #STOPWORDS_COMMENT}
+ * @deprecated use {@link #ArabicAnalyzer(Version, Set)} instead
+ */
+ @Deprecated
+ public ArabicAnalyzer( Version matchVersion, File stopwords ) throws IOException {
+ this(matchVersion, WordlistLoader.getWordSet(IOUtils.getDecodingReader(stopwords,
+ IOUtils.CHARSET_UTF_8), STOPWORDS_COMMENT, matchVersion));
+ }
+
+ /**
+ * Creates
+ * {@link org.apache.lucene.analysis.ReusableAnalyzerBase.TokenStreamComponents}
+ * used to tokenize all the text in the provided {@link Reader}.
+ *
+ * @return {@link org.apache.lucene.analysis.ReusableAnalyzerBase.TokenStreamComponents}
+ * built from an {@link StandardTokenizer} filtered with
+ * {@link LowerCaseFilter}, {@link StopFilter},
+ * {@link ArabicNormalizationFilter}, {@link KeywordMarkerFilter}
+ * if a stem exclusion set is provided and {@link ArabicStemFilter}.
+ */
+ @Override
+ protected TokenStreamComponents createComponents(String fieldName,
+ Reader reader) {
+ final Tokenizer source = matchVersion.onOrAfter(Version.LUCENE_31) ?
+ new StandardTokenizer(matchVersion, reader) : new ArabicLetterTokenizer(matchVersion, reader);
+ TokenStream result = new LowerCaseFilter(matchVersion, source);
+ // the order here is important: the stopword list is not normalized!
+ result = new StopFilter( matchVersion, result, stopwords);
+ // TODO maybe we should make ArabicNormalization filter also KeywordAttribute aware?!
+ result = new ArabicNormalizationFilter(result);
+ if(!stemExclusionSet.isEmpty()) {
+ result = new KeywordMarkerFilter(result, stemExclusionSet);
+ }
+ return new TokenStreamComponents(source, new ArabicStemFilter(result));
+ }
+}
+
fnp / pylucene.git / blobdiff