org.apache.logging.log4j.util.LoaderUtil Maven / Gradle / Ivy
/*
* 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.logging.log4j.util;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.net.URL;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Collection;
import java.util.Enumeration;
import java.util.LinkedHashSet;
/**
* Consider this class private. Utility class for ClassLoaders.
* @see ClassLoader
* @see RuntimePermission
* @see Thread#getContextClassLoader()
* @see ClassLoader#getSystemClassLoader()
*/
public final class LoaderUtil {
private LoaderUtil() {}
/**
* System property to set to ignore the thread context ClassLoader.
*
* @since 2.1
*/
public static final String IGNORE_TCCL_PROPERTY = "log4j.ignoreTCL";
private static final SecurityManager SECURITY_MANAGER = System.getSecurityManager();
// this variable must be lazily loaded; otherwise, we get a nice circular class loading problem where LoaderUtil
// wants to use PropertiesUtil, but then PropertiesUtil wants to use LoaderUtil.
private static Boolean ignoreTCCL;
private static final boolean GET_CLASS_LOADER_DISABLED;
private static final PrivilegedAction TCCL_GETTER = new ThreadContextClassLoaderGetter();
static {
if (SECURITY_MANAGER != null) {
boolean getClassLoaderDisabled;
try {
SECURITY_MANAGER.checkPermission(new RuntimePermission("getClassLoader"));
getClassLoaderDisabled = false;
} catch (final SecurityException ignored) {
getClassLoaderDisabled = true;
}
GET_CLASS_LOADER_DISABLED = getClassLoaderDisabled;
} else {
GET_CLASS_LOADER_DISABLED = false;
}
}
/**
* Gets the current Thread ClassLoader. Returns the system ClassLoader if the TCCL is {@code null}. If the
* system ClassLoader is {@code null} as well, then the ClassLoader for this class is returned.
* If running with a {@link SecurityManager} that does not allow access to the Thread ClassLoader or system
* ClassLoader, then the ClassLoader for this class is returned.
*
* @return the current ThreadContextClassLoader.
*/
public static ClassLoader getThreadContextClassLoader() {
if (GET_CLASS_LOADER_DISABLED) {
// we can at least get this class's ClassLoader regardless of security context
// however, if this is null, there's really no option left at this point
return LoaderUtil.class.getClassLoader();
}
return SECURITY_MANAGER == null
? TCCL_GETTER.run()
: AccessController.doPrivileged(TCCL_GETTER);
}
private static class ThreadContextClassLoaderGetter implements PrivilegedAction {
@Override
public ClassLoader run() {
final ClassLoader cl = Thread.currentThread().getContextClassLoader();
if (cl != null) {
return cl;
}
final ClassLoader ccl = LoaderUtil.class.getClassLoader();
return ccl == null ? ClassLoader.getSystemClassLoader() : ccl;
}
}
/**
* Loads a class by name. This method respects the {@link #IGNORE_TCCL_PROPERTY} Log4j property. If this property
* is specified and set to anything besides {@code false}, then the default ClassLoader will be used.
*
* @param className The class name.
* @return the Class for the given name.
* @throws ClassNotFoundException if the specified class name could not be found
* @since 2.1
*/
public static Class loadClass(final String className) throws ClassNotFoundException {
if (isIgnoreTccl()) {
return Class.forName(className);
}
try {
return getThreadContextClassLoader().loadClass(className);
} catch (final Throwable ignored) {
return Class.forName(className);
}
}
/**
* Loads and instantiates a Class using the default constructor.
*
* @param className The class name.
* @return new instance of the class.
* @throws ClassNotFoundException if the class isn't available to the usual ClassLoaders
* @throws IllegalAccessException if the class can't be instantiated through a public constructor
* @throws InstantiationException if there was an exception whilst instantiating the class
* @throws NoSuchMethodException if there isn't a no-args constructor on the class
* @throws InvocationTargetException if there was an exception whilst constructing the class
* @since 2.1
*/
public static Object newInstanceOf(final String className)
throws ClassNotFoundException, IllegalAccessException, InstantiationException, NoSuchMethodException,
InvocationTargetException {
final Class clazz = loadClass(className);
try {
return clazz.getConstructor().newInstance();
} catch (final NoSuchMethodException ignored) {
// FIXME: looking at the code for Class.newInstance(), this seems to do the same thing as above
return clazz.newInstance();
}
}
/**
* Loads and instantiates a derived class using its default constructor.
*
* @param className The class name.
* @param clazz The class to cast it to.
* @param The type of the class to check.
* @return new instance of the class cast to {@code T}
* @throws ClassNotFoundException if the class isn't available to the usual ClassLoaders
* @throws IllegalAccessException if the class can't be instantiated through a public constructor
* @throws InstantiationException if there was an exception whilst instantiating the class
* @throws NoSuchMethodException if there isn't a no-args constructor on the class
* @throws InvocationTargetException if there was an exception whilst constructing the class
* @throws ClassCastException if the constructed object isn't type compatible with {@code T}
* @since 2.1
*/
public static T newCheckedInstanceOf(final String className, final Class clazz)
throws ClassNotFoundException, NoSuchMethodException, InvocationTargetException, InstantiationException,
IllegalAccessException {
return clazz.cast(newInstanceOf(className));
}
private static boolean isIgnoreTccl() {
// we need to lazily initialize this, but concurrent access is not an issue
if (ignoreTCCL == null) {
final String ignoreTccl = PropertiesUtil.getProperties().getStringProperty(IGNORE_TCCL_PROPERTY, null);
ignoreTCCL = ignoreTccl != null && !"false".equalsIgnoreCase(ignoreTccl.trim());
}
return ignoreTCCL;
}
/**
* Finds classpath {@linkplain URL resources}.
*
* @param resource the name of the resource to find.
* @return a Collection of URLs matching the resource name. If no resources could be found, then this will be empty.
* @since 2.1
*/
public static Collection findResources(final String resource) {
final Collection urlResources = findUrlResources(resource);
final Collection resources = new LinkedHashSet(urlResources.size());
for (final UrlResource urlResource : urlResources) {
resources.add(urlResource.getUrl());
}
return resources;
}
static Collection findUrlResources(final String resource) {
final ClassLoader[] candidates = {
getThreadContextClassLoader(),
LoaderUtil.class.getClassLoader(),
ClassLoader.getSystemClassLoader()
};
final Collection resources = new LinkedHashSet();
for (final ClassLoader cl : candidates) {
if (cl != null) {
try {
final Enumeration resourceEnum = cl.getResources(resource);
while (resourceEnum.hasMoreElements()) {
resources.add(new UrlResource(cl, resourceEnum.nextElement()));
}
} catch (final IOException e) {
e.printStackTrace();
}
}
}
return resources;
}
/**
* {@link URL} and {@link ClassLoader} pair.
*/
static class UrlResource {
private final ClassLoader classLoader;
private final URL url;
public UrlResource(final ClassLoader classLoader, final URL url) {
this.classLoader = classLoader;
this.url = url;
}
public ClassLoader getClassLoader() {
return classLoader;
}
public URL getUrl() {
return url;
}
@Override
public boolean equals(final Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
final UrlResource that = (UrlResource) o;
if (classLoader != null ? !classLoader.equals(that.classLoader) : that.classLoader != null) {
return false;
}
if (url != null ? !url.equals(that.url) : that.url != null) {
return false;
}
return true;
}
@Override
public int hashCode() {
int result = classLoader != null ? classLoader.hashCode() : 0;
result = 31 * result + (url != null ? url.hashCode() : 0);
return result;
}
}
}