/*
* 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.webapp.common;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.Iterator;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.nutch.plugin.Extension;
import org.apache.nutch.plugin.ExtensionPoint;
import org.apache.nutch.plugin.PluginClassLoader;
import org.apache.nutch.util.LogUtil;
import org.apache.nutch.webapp.extension.UIExtensionPoint;
/**
* PluginResourceLoader is capable of loading plugged in resources.
*/
public class PluginResourceLoader extends ClassLoader {
public class ThrowAwayClassLoader extends ClassLoader {
private ClassLoader one;
private ClassLoader two;
public ThrowAwayClassLoader(ClassLoader two, ClassLoader one) {
this.one = one;
this.two = two;
}
/*
* (non-Javadoc)
*
* @see java.lang.ClassLoader#getResource(java.lang.String)
*/
public URL getResource(String name) {
URL retVal = one.getResource(name);
if (retVal == null)
retVal = two.getResource(name);
return retVal;
}
/*
* (non-Javadoc)
*
* @see java.lang.ClassLoader#getResourceAsStream(java.lang.String)
*/
public InputStream getResourceAsStream(String name) {
InputStream retVal = one.getResourceAsStream(name);
if (retVal == null)
retVal = two.getResourceAsStream(name);
return retVal;
}
/*
* (non-Javadoc)
*
* @see java.lang.ClassLoader#getResources(java.lang.String)
*/
public Enumeration getResources(String name) throws IOException {
Enumeration retVal = one.getResources(name);
if (retVal == null)
retVal = two.getResources(name);
return retVal;
}
/*
* (non-Javadoc)
*
* @see java.lang.ClassLoader#loadClass(java.lang.String)
*/
public Class loadClass(String name) throws ClassNotFoundException {
if(LOG.isDebugEnabled()){
LOG.debug("loading class " + name + " from " + one);
}
try {
return one.loadClass(name);
} catch (ClassNotFoundException e) {
}
if(LOG.isDebugEnabled()){
LOG.debug("loading class " + name + " from " + two);
}
try {
return two.loadClass(name);
} catch (ClassNotFoundException e) {
}
if(LOG.isDebugEnabled()){
LOG.info("could not find class, must throw Exception");
}
throw new ClassNotFoundException(name);
}
}
ClassLoader wrapped;
ArrayList classloaders = new ArrayList();
public static Log LOG = LogFactory.getLog(PluginResourceLoader.class);
public static PluginResourceLoader getInstance(ServiceLocator locator,
ClassLoader parent) {
PluginResourceLoader loader = (PluginResourceLoader) locator
.getConfiguration().getObject(PluginResourceLoader.class.getName());
if (loader == null) {
LOG.info("Created new nutch loader with parent loader:" + parent);
loader = new PluginResourceLoader(locator, parent);
locator.getConfiguration().setObject(
PluginResourceLoader.class.getName(), loader);
}
return loader;
}
private PluginResourceLoader(ServiceLocator locator, ClassLoader parent) {
init(locator, parent);
}
protected void init(ServiceLocator locator, ClassLoader parent) {
ArrayList seen = new ArrayList();
ArrayList paths = new ArrayList();
if (LOG.isDebugEnabled()) {
LOG.debug("PluginResourceLoader : dynamically setting jars based "
+ "on plugins implementing UIExtensionPoint.");
}
ExtensionPoint point = locator.getPluginRepository().getExtensionPoint(
UIExtensionPoint.X_POINT_ID);
if (point == null) {
LOG.info("Can't find extension point '" + UIExtensionPoint.X_POINT_ID
+ "'");
classloaders.add(parent);
return;
}
Extension[] extensions = point.getExtensions();
for (int i = 0; i < extensions.length; i++) {
Extension extension = extensions[i];
PluginClassLoader loader = extension.getDescriptor().getClassLoader();
// classloaders.add(loader);
URL[] urls = loader.getURLs();
for (int k = 0; k < urls.length; k++) {
URL url = urls[k];
if (!seen.contains(url)) {
paths.add(url);
LOG.debug("Adding to classpath:" + url);
}
seen.add(url);
}
}
URL[] urls = (URL[]) paths.toArray(new URL[paths.size()]);
classloaders.add(new URLClassLoader(urls, parent));
}
public URL getResource(String name) {
Iterator i = classloaders.iterator();
while (i.hasNext()) {
ClassLoader loader = (ClassLoader) i.next();
URL retVal = loader.getResource(name);
if (retVal != null) {
return retVal;
}
}
return null;
}
public InputStream getResourceAsStream(String name) {
Iterator i = classloaders.iterator();
while (i.hasNext()) {
ClassLoader loader = (ClassLoader) i.next();
InputStream retVal = loader.getResourceAsStream(name);
if (retVal != null) {
return retVal;
}
}
return null;
}
public Enumeration getResources(String name) throws IOException {
Iterator i = classloaders.iterator();
while (i.hasNext()) {
ClassLoader loader = (ClassLoader) i.next();
Enumeration retVal = loader.getResources(name);
if (retVal != null) {
return retVal;
}
}
return null;
}
public Class loadClass(String name) throws ClassNotFoundException {
try {
// LOG.info("CUSTOM_LOADER->load");
Iterator i = classloaders.iterator();
Class retVal = null;
while (i.hasNext()) {
ClassLoader loader = (ClassLoader) i.next();
// LOG.info("trying to load " + name + " from:" + loader);
try {
retVal = loader.loadClass(name);
} catch (Exception e) {
LOG.info("Exception in loader " + e);
}
if (retVal != null) {
// LOG.info("CUSTOM_LOADER->found");
return retVal;
}
}
// LOG.info("CUSTOM_LOADER_not found");
} catch (Exception e) {
LOG.info("Exception in loader " + e);
e.printStackTrace(LogUtil.getInfoStream(LOG));
}
throw new ClassNotFoundException(name);
}
}