/**
* 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.protocol;
import java.net.URL;
import java.net.MalformedURLException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.nutch.plugin.*;
import org.apache.nutch.util.ObjectCache;
import org.apache.hadoop.conf.Configuration;
/**
* Creates and caches {@link Protocol} plugins. Protocol plugins should define
* the attribute "protocolName" with the name of the protocol that they
* implement. Configuration object is used for caching. Cache key is constructed
* from appending protocol name (eg. http) to constant
* {@link Protocol#X_POINT_ID}.
*/
public class ProtocolFactory {
public static final Logger LOG = LoggerFactory.getLogger(ProtocolFactory.class);
private ExtensionPoint extensionPoint;
private Configuration conf;
public ProtocolFactory(Configuration conf) {
this.conf = conf;
this.extensionPoint = PluginRepository.get(conf).getExtensionPoint(
Protocol.X_POINT_ID);
if (this.extensionPoint == null) {
throw new RuntimeException("x-point " + Protocol.X_POINT_ID
+ " not found.");
}
}
/**
* Returns the appropriate {@link Protocol} implementation for a url.
*
* @param urlString
* Url String
* @return The appropriate {@link Protocol} implementation for a given
* {@link URL}.
* @throws ProtocolNotFound
* when Protocol can not be found for urlString
*/
public synchronized Protocol getProtocol(String urlString)
throws ProtocolNotFound {
ObjectCache objectCache = ObjectCache.get(conf);
try {
URL url = new URL(urlString);
String protocolName = url.getProtocol();
if (protocolName == null)
throw new ProtocolNotFound(urlString);
String cacheId = Protocol.X_POINT_ID + protocolName;
Protocol protocol = (Protocol) objectCache.getObject(cacheId);
if (protocol != null) {
return protocol;
}
Extension extension = findExtension(protocolName);
if (extension == null) {
throw new ProtocolNotFound(protocolName);
}
protocol = (Protocol) extension.getExtensionInstance();
objectCache.setObject(cacheId, protocol);
return protocol;
} catch (MalformedURLException e) {
throw new ProtocolNotFound(urlString, e.toString());
} catch (PluginRuntimeException e) {
throw new ProtocolNotFound(urlString, e.toString());
}
}
private Extension findExtension(String name) throws PluginRuntimeException {
Extension[] extensions = this.extensionPoint.getExtensions();
for (int i = 0; i < extensions.length; i++) {
Extension extension = extensions[i];
if (contains(name, extension.getAttribute("protocolName")))
return extension;
}
return null;
}
boolean contains(String what, String where) {
String parts[] = where.split("[, ]");
for (int i = 0; i < parts.length; i++) {
if (parts[i].equals(what))
return true;
}
return false;
}
}