/**
* 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.hadoop.util;
import java.io.File;
import java.io.FilenameFilter;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Properties;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience.Public;
import org.apache.hadoop.classification.InterfaceStability.Unstable;
/**
* A {@link URLClassLoader} for application isolation. Classes from the
* application JARs are loaded in preference to the parent loader.
*/
@Public
@Unstable
public class ApplicationClassLoader extends URLClassLoader {
/**
* Default value of the system classes if the user did not override them.
* JDK classes, hadoop classes and resources, and some select third-party
* classes are considered system classes, and are not loaded by the
* application classloader.
*/
public static final String SYSTEM_CLASSES_DEFAULT;
private static final String PROPERTIES_FILE =
"org.apache.hadoop.application-classloader.properties";
private static final String SYSTEM_CLASSES_DEFAULT_KEY =
"system.classes.default";
private static final Log LOG =
LogFactory.getLog(ApplicationClassLoader.class.getName());
private static final FilenameFilter JAR_FILENAME_FILTER =
new FilenameFilter() {
@Override
public boolean accept(File dir, String name) {
return name.endsWith(".jar") || name.endsWith(".JAR");
}
};
static {
try (InputStream is = ApplicationClassLoader.class.getClassLoader()
.getResourceAsStream(PROPERTIES_FILE);) {
if (is == null) {
throw new ExceptionInInitializerError("properties file " +
PROPERTIES_FILE + " is not found");
}
Properties props = new Properties();
props.load(is);
// get the system classes default
String systemClassesDefault =
props.getProperty(SYSTEM_CLASSES_DEFAULT_KEY);
if (systemClassesDefault == null) {
throw new ExceptionInInitializerError("property " +
SYSTEM_CLASSES_DEFAULT_KEY + " is not found");
}
SYSTEM_CLASSES_DEFAULT = systemClassesDefault;
} catch (IOException e) {
throw new ExceptionInInitializerError(e);
}
}
private final ClassLoader parent;
private final List<String> systemClasses;
public ApplicationClassLoader(URL[] urls, ClassLoader parent,
List<String> systemClasses) {
super(urls, parent);
if (LOG.isDebugEnabled()) {
LOG.debug("urls: " + Arrays.toString(urls));
LOG.debug("system classes: " + systemClasses);
}
this.parent = parent;
if (parent == null) {
throw new IllegalArgumentException("No parent classloader!");
}
// if the caller-specified system classes are null or empty, use the default
this.systemClasses = (systemClasses == null || systemClasses.isEmpty()) ?
Arrays.asList(StringUtils.getTrimmedStrings(SYSTEM_CLASSES_DEFAULT)) :
systemClasses;
LOG.info("system classes: " + this.systemClasses);
}
public ApplicationClassLoader(String classpath, ClassLoader parent,
List<String> systemClasses) throws MalformedURLException {
this(constructUrlsFromClasspath(classpath), parent, systemClasses);
}
static URL[] constructUrlsFromClasspath(String classpath)
throws MalformedURLException {
List<URL> urls = new ArrayList<URL>();
for (String element : classpath.split(File.pathSeparator)) {
if (element.endsWith("/*")) {
String dir = element.substring(0, element.length() - 1);
File[] files = new File(dir).listFiles(JAR_FILENAME_FILTER);
if (files != null) {
for (File file : files) {
urls.add(file.toURI().toURL());
}
}
} else {
File file = new File(element);
if (file.exists()) {
urls.add(new File(element).toURI().toURL());
}
}
}
return urls.toArray(new URL[urls.size()]);
}
@Override
public URL getResource(String name) {
URL url = null;
if (!isSystemClass(name, systemClasses)) {
url= findResource(name);
if (url == null && name.startsWith("/")) {
if (LOG.isDebugEnabled()) {
LOG.debug("Remove leading / off " + name);
}
url= findResource(name.substring(1));
}
}
if (url == null) {
url= parent.getResource(name);
}
if (url != null) {
if (LOG.isDebugEnabled()) {
LOG.debug("getResource("+name+")=" + url);
}
}
return url;
}
@Override
public Class<?> loadClass(String name) throws ClassNotFoundException {
return this.loadClass(name, false);
}
@Override
protected synchronized Class<?> loadClass(String name, boolean resolve)
throws ClassNotFoundException {
if (LOG.isDebugEnabled()) {
LOG.debug("Loading class: " + name);
}
Class<?> c = findLoadedClass(name);
ClassNotFoundException ex = null;
if (c == null && !isSystemClass(name, systemClasses)) {
// Try to load class from this classloader's URLs. Note that this is like
// the servlet spec, not the usual Java 2 behaviour where we ask the
// parent to attempt to load first.
try {
c = findClass(name);
if (LOG.isDebugEnabled() && c != null) {
LOG.debug("Loaded class: " + name + " ");
}
} catch (ClassNotFoundException e) {
if (LOG.isDebugEnabled()) {
LOG.debug(e);
}
ex = e;
}
}
if (c == null) { // try parent
c = parent.loadClass(name);
if (LOG.isDebugEnabled() && c != null) {
LOG.debug("Loaded class from parent: " + name + " ");
}
}
if (c == null) {
throw ex != null ? ex : new ClassNotFoundException(name);
}
if (resolve) {
resolveClass(c);
}
return c;
}
/**
* Checks if a class should be included as a system class.
*
* A class is a system class if and only if it matches one of the positive
* patterns and none of the negative ones.
*
* @param name the class name to check
* @param systemClasses a list of system class configurations.
* @return true if the class is a system class
*/
public static boolean isSystemClass(String name, List<String> systemClasses) {
boolean result = false;
if (systemClasses != null) {
String canonicalName = name.replace('/', '.');
while (canonicalName.startsWith(".")) {
canonicalName=canonicalName.substring(1);
}
for (String c : systemClasses) {
boolean shouldInclude = true;
if (c.startsWith("-")) {
c = c.substring(1);
shouldInclude = false;
}
if (canonicalName.startsWith(c)) {
if ( c.endsWith(".") // package
|| canonicalName.length() == c.length() // class
|| canonicalName.length() > c.length() // nested
&& canonicalName.charAt(c.length()) == '$' ) {
if (shouldInclude) {
result = true;
} else {
return false;
}
}
}
}
}
return result;
}
}