/**
* 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.nutch.crawl;
// Commons Logging imports
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
// Hadoop imports
import org.apache.hadoop.conf.Configuration;
import org.apache.nutch.util.ObjectCache;
/**
* Factory class, which instantiates a Signature implementation according to the
* current Configuration configuration. This newly created instance is cached in the
* Configuration instance, so that it could be later retrieved.
*
* @author Andrzej Bialecki <ab@getopt.org>
*/
public class SignatureFactory {
private static final Logger LOG = LoggerFactory.getLogger(SignatureFactory.class);
private SignatureFactory() {} // no public ctor
/** Return the default Signature implementation. */
public synchronized static Signature getSignature(Configuration conf) {
String clazz = conf.get("db.signature.class", MD5Signature.class.getName());
ObjectCache objectCache = ObjectCache.get(conf);
Signature impl = (Signature)objectCache.getObject(clazz);
if (impl == null) {
try {
if (LOG.isInfoEnabled()) {
LOG.info("Using Signature impl: " + clazz);
}
Class<?> implClass = Class.forName(clazz);
impl = (Signature)implClass.newInstance();
impl.setConf(conf);
objectCache.setObject(clazz, impl);
} catch (Exception e) {
throw new RuntimeException("Couldn't create " + clazz, e);
}
}
return impl;
}
}