org.apache.logging.log4j.util.LoaderUtil Maven / Gradle / Ivy

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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;
        }
    }
}