ClassLoaderUtils.java
/**
* 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.cxf.common.classloader;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLClassLoader;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;
/**
* This class is extremely useful for loading resources and classes in a fault
* tolerant manner that works across different applications servers. Do not
* touch this unless you're a grizzled classloading guru veteran who is going to
* verify any change on 6 different application servers.
*/
public final class ClassLoaderUtils {
private static final boolean SKIP_SM = System.getSecurityManager() == null;
private ClassLoaderUtils() {
}
public static class ClassLoaderHolder {
ClassLoader loader;
Thread thread;
ClassLoaderHolder(final ClassLoader c, final Thread thread) {
this.loader = c;
this.thread = thread;
}
public void reset() {
if (SKIP_SM) {
thread.setContextClassLoader(loader);
} else {
AccessController.doPrivileged(new PrivilegedAction<Void>() {
public Void run() {
thread.setContextClassLoader(loader);
return null;
}
});
}
}
}
public static ClassLoaderHolder setThreadContextClassloader(final ClassLoader newLoader) {
if (SKIP_SM) {
final Thread thread = Thread.currentThread();
final ClassLoader l = thread.getContextClassLoader();
thread.setContextClassLoader(newLoader);
return new ClassLoaderHolder(l, thread);
}
return AccessController.doPrivileged(new PrivilegedAction<ClassLoaderHolder>() {
public ClassLoaderHolder run() {
final Thread thread = Thread.currentThread();
final ClassLoader l = thread.getContextClassLoader();
thread.setContextClassLoader(newLoader);
return new ClassLoaderHolder(l, thread);
}
});
}
public static ClassLoader getURLClassLoader(
final URL[] urls, final ClassLoader parent
) {
return AccessController.doPrivileged(new PrivilegedAction<ClassLoader>() {
public ClassLoader run() {
return new URLClassLoader(urls, parent);
}
});
}
public static ClassLoader getURLClassLoader(
final List<URL> urlList, final ClassLoader parent
) {
return getURLClassLoader(urlList.toArray(new URL[0]), parent);
}
/**
* Load a given resource. <p/> This method will try to load the resource
* using the following methods (in order):
* <ul>
* <li>From Thread.currentThread().getContextClassLoader()
* <li>From ClassLoaderUtil.class.getClassLoader()
* <li>callingClass.getClassLoader()
* </ul>
*
* @param resourceName The name of the resource to load
* @param callingClass The Class object of the calling object
*/
public static URL getResource(String resourceName, Class<?> callingClass) {
ClassLoader contextClassLoader = getContextClassLoader();
URL url = contextClassLoader.getResource(resourceName);
if (url == null && resourceName.startsWith("/")) {
//certain classloaders need it without the leading /
url = contextClassLoader.getResource(resourceName.substring(1));
}
ClassLoader cluClassloader = ClassLoaderUtils.class.getClassLoader();
if (cluClassloader == null) {
cluClassloader = ClassLoader.getSystemClassLoader();
}
if (url == null) {
url = cluClassloader.getResource(resourceName);
}
if (url == null && resourceName.startsWith("/")) {
//certain classloaders need it without the leading /
url = cluClassloader.getResource(resourceName.substring(1));
}
if (url == null && callingClass != null) {
ClassLoader cl = callingClass.getClassLoader();
if (cl != null) {
url = cl.getResource(resourceName);
}
}
if (url == null && callingClass != null) {
url = callingClass.getResource(resourceName);
}
if ((url == null) && (resourceName.charAt(0) != '/')) {
return getResource('/' + resourceName, callingClass);
}
return url;
}
/**
* Load a given resources. <p/> This method will try to load the resources
* using the following methods (in order):
* <ul>
* <li>From Thread.currentThread().getContextClassLoader()
* <li>From ClassLoaderUtil.class.getClassLoader()
* <li>callingClass.getClassLoader()
* </ul>
*
* @param resourceName The name of the resource to load
* @param callingClass The Class object of the calling object
*/
public static List<URL> getResources(String resourceName, Class<?> callingClass) {
List<URL> ret = new ArrayList<>();
Enumeration<URL> urls = new Enumeration<URL>() {
public boolean hasMoreElements() {
return false;
}
public URL nextElement() {
return null;
}
};
try {
urls = getContextClassLoader().getResources(resourceName);
} catch (IOException e) {
//ignore
}
if (!urls.hasMoreElements() && resourceName.startsWith("/")) {
//certain classloaders need it without the leading /
try {
urls = getContextClassLoader().getResources(resourceName.substring(1));
} catch (IOException e) {
// ignore
}
}
ClassLoader cluClassloader = ClassLoaderUtils.class.getClassLoader();
if (cluClassloader == null) {
cluClassloader = ClassLoader.getSystemClassLoader();
}
if (!urls.hasMoreElements()) {
try {
urls = cluClassloader.getResources(resourceName);
} catch (IOException e) {
// ignore
}
}
if (!urls.hasMoreElements() && resourceName.startsWith("/")) {
//certain classloaders need it without the leading /
try {
urls = cluClassloader.getResources(resourceName.substring(1));
} catch (IOException e) {
// ignore
}
}
if (!urls.hasMoreElements()) {
ClassLoader cl = callingClass.getClassLoader();
if (cl != null) {
try {
urls = cl.getResources(resourceName);
} catch (IOException e) {
// ignore
}
}
}
if (!urls.hasMoreElements()) {
URL url = callingClass.getResource(resourceName);
if (url != null) {
ret.add(url);
}
}
while (urls.hasMoreElements()) {
ret.add(urls.nextElement());
}
if (ret.isEmpty() && (resourceName.charAt(0) != '/')) {
return getResources('/' + resourceName, callingClass);
}
return ret;
}
/**
* This is a convenience method to load a resource as a stream. <p/> The
* algorithm used to find the resource is given in getResource()
*
* @param resourceName The name of the resource to load
* @param callingClass The Class object of the calling object
*/
public static InputStream getResourceAsStream(String resourceName, Class<?> callingClass) {
URL url = getResource(resourceName, callingClass);
try {
return (url != null) ? url.openStream() : null;
} catch (IOException e) {
return null;
}
}
/**
* Load a class with a given name. <p/> It will try to load the class in the
* following order:
* <ul>
* <li>From Thread.currentThread().getContextClassLoader()
* <li>Using the basic Class.forName()
* <li>From ClassLoaderUtil.class.getClassLoader()
* <li>From the callingClass.getClassLoader()
* </ul>
*
* @param className The name of the class to load
* @param callingClass The Class object of the calling object
* @throws ClassNotFoundException If the class cannot be found anywhere.
*/
public static Class<?> loadClass(String className, Class<?> callingClass)
throws ClassNotFoundException {
try {
ClassLoader cl = getContextClassLoader();
if (cl != null) {
return cl.loadClass(className);
}
} catch (ClassNotFoundException e) {
//ignore
}
return loadClass2(className, callingClass);
}
public static <T> Class<? extends T> loadClass(String className, Class<?> callingClass, Class<T> type)
throws ClassNotFoundException {
try {
ClassLoader cl = getContextClassLoader();
if (cl != null) {
return cl.loadClass(className).asSubclass(type);
}
} catch (ClassNotFoundException e) {
//ignore
}
return loadClass2(className, callingClass).asSubclass(type);
}
public static String getClassLoaderName(Class<?> type) {
ClassLoader loader = getClassLoader(type);
return loader == null ? "null" : loader.toString();
}
public static Class<?> loadClassFromContextLoader(String className) throws ClassNotFoundException {
return getContextClassLoader().loadClass(className);
}
private static Class<?> loadClass2(String className, Class<?> callingClass)
throws ClassNotFoundException {
try {
return Class.forName(className);
} catch (ClassNotFoundException ex) {
try {
final ClassLoader loader = getClassLoader(ClassLoaderUtils.class);
if (loader != null) {
return loader.loadClass(className);
}
} catch (ClassNotFoundException exc) {
if (callingClass != null) {
final ClassLoader callingClassLoader = getClassLoader(callingClass);
if (callingClassLoader != null) {
return callingClassLoader.loadClass(className);
}
}
}
throw ex;
}
}
static ClassLoader getContextClassLoader() {
final SecurityManager sm = System.getSecurityManager();
if (sm != null) {
return AccessController.doPrivileged(new PrivilegedAction<ClassLoader>() {
public ClassLoader run() {
ClassLoader loader = Thread.currentThread().getContextClassLoader();
return loader != null ? loader : ClassLoader.getSystemClassLoader();
}
});
}
ClassLoader loader = Thread.currentThread().getContextClassLoader();
return loader != null ? loader : ClassLoader.getSystemClassLoader();
}
private static ClassLoader getClassLoader(final Class<?> clazz) {
final SecurityManager sm = System.getSecurityManager();
if (sm != null) {
return AccessController.doPrivileged(new PrivilegedAction<ClassLoader>() {
public ClassLoader run() {
return clazz.getClassLoader();
}
});
}
return clazz.getClassLoader();
}
}