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Pax Logging backend implementation based on Apache Log4J2. It provides Log4J2 specific implementation of PaxLoggingService interface and Log4J2 specific configuration methods. Users may customize Log4J2 behaviour (appenders, layouts) by creating fragment attached to this bundle.

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/*
 * 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.security.AccessController;
import java.security.PrivilegedAction;

/**
 * Consider this class private. Utility class for ClassLoaders.
 * @see ClassLoader
 * @see Thread#getContextClassLoader()
 */
// TODO: migrate any other useful methods from Loader in log4j-core
public final class LoaderUtil {
    private LoaderUtil() {}

    private static final PrivilegedAction TCCL_GETTER = new ThreadContextClassLoaderGetter();

    static {
        final SecurityManager sm = System.getSecurityManager();
        if (sm != null) {
            sm.checkPermission(new RuntimePermission("getClassLoader"));
        }
    }

    /**
     * Gets the current Thread ClassLoader. Returns the system ClassLoader if the TCCL is {@code null}.
     *
     * @return the current ThreadContextClassLoader.
     */
    public static ClassLoader getThreadContextClassLoader() {
        return System.getSecurityManager() == 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 the TCCL is null, that means we're using the system CL
            return cl == null ? ClassLoader.getSystemClassLoader() : cl;
        }
    }
}