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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
/*
* 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.cassandra.index.sasi.analyzer.filter;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Locale;
import java.util.Set;
import java.util.concurrent.CompletionException;
import com.github.benmanes.caffeine.cache.Caffeine;
import com.github.benmanes.caffeine.cache.LoadingCache;
import org.apache.cassandra.concurrent.ImmediateExecutor;
import org.apache.cassandra.io.util.File;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Provides a list of Stop Words for a given language
*/
public class StopWordFactory
{
private static final Logger logger = LoggerFactory.getLogger(StopWordFactory.class);
private static final String DEFAULT_RESOURCE_EXT = "_ST.txt";
private static final String DEFAULT_RESOURCE_PREFIX = StopWordFactory.class.getPackage()
.getName().replace(".", File.pathSeparator());
private static final Set SUPPORTED_LANGUAGES = new HashSet<>(
Arrays.asList("ar","bg","cs","de","en","es","fi","fr","hi","hu","it",
"pl","pt","ro","ru","sv"));
private static final LoadingCache> STOP_WORDS_CACHE = Caffeine.newBuilder()
.executor(ImmediateExecutor.INSTANCE)
.build(StopWordFactory::getStopWordsFromResource);
public static Set getStopWordsForLanguage(Locale locale)
{
if (locale == null)
return null;
String rootLang = locale.getLanguage().substring(0, 2);
try
{
return (!SUPPORTED_LANGUAGES.contains(rootLang)) ? null : STOP_WORDS_CACHE.get(rootLang);
}
catch (CompletionException e)
{
logger.error("Failed to populate Stop Words Cache for language [{}]", locale.getLanguage(), e);
return null;
}
}
private static Set getStopWordsFromResource(String language)
{
Set stopWords = new HashSet<>();
String resourceName = DEFAULT_RESOURCE_PREFIX + File.pathSeparator() + language + DEFAULT_RESOURCE_EXT;
try (InputStream is = StopWordFactory.class.getClassLoader().getResourceAsStream(resourceName);
BufferedReader r = new BufferedReader(new InputStreamReader(is, StandardCharsets.UTF_8)))
{
String line;
while ((line = r.readLine()) != null)
{
//skip comments (lines starting with # char)
if(line.charAt(0) == '#')
continue;
stopWords.add(line.trim());
}
}
catch (Exception e)
{
logger.error("Failed to retrieve Stop Terms resource for language [{}]", language, e);
}
return stopWords;
}
}