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Apache Log4j 1.2 compatible logging API
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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.log4j;

import java.util.Hashtable;

import org.tinylog.ThreadContext;

/**
 * The MDC class is similar to the {@link NDC} class except that it is based on a map instead of a stack. It provides
 * mapped diagnostic contexts. A Mapped Diagnostic Context, or MDC in short, is an instrument for
 * distinguishing interleaved log output from different sources. Log output is typically interleaved when a server
 * handles multiple clients near-simultaneously.
 * 
 * 
 * The MDC is managed on a per thread basis. A child thread automatically inherits a copy of
 * the mapped diagnostic context of its parent.
 * 
 * 
 * 
 * The MDC class requires JDK 1.2 or above. Under JDK 1.1 the MDC will always return empty values but otherwise will not
 * affect or harm your application.
 * 
 * 
 * @author Ceki Gülcü
 * @since 1.2
 */
public final class MDC {

	/** */
	private MDC() {
	}

	/**
	 * Get the current thread's MDC as a hashtable. This method is intended to be used internally.
	 * 
	 * @return Copy of all actual context values
	 */
	@SuppressWarnings({ "rawtypes", "unchecked" })
	public static Hashtable getContext() {
		return new Hashtable(ThreadContext.getMapping());
	}

	/**
	 * Get the context identified by the {@code key} parameter.
	 * 
	 * 
	 * This method has no side effects.
	 * 
	 * 
	 * @param key
	 *            Key parameter of context value
	 * @return Context value
	 */
	public static Object get(final String key) {
		return ThreadContext.get(key);
	}

	/**
	 * Put a context value (the {@code o} parameter) as identified with the {@code key} parameter into the current
	 * thread's context map.
	 * 
	 * 
	 * If the current thread does not have a context map it is created as a side effect.
	 * 
	 *
	 * @param key
	 *            Key parameter of context value
	 * @param value
	 *            Context value
	 */
	public static void put(final String key, final Object value) {
		ThreadContext.put(key, value);
	}

	/**
	 * Remove the the context identified by the {@code key} parameter.
	 *
	 * @param key
	 *            Key of parameter to remove
	 */
	public static void remove(final String key) {
		ThreadContext.remove(key);
	}

	/**
	 * Remove all values from the MDC.
	 * 
	 * @since 1.2.16
	 */
	public static void clear() {
		ThreadContext.clear();
	}

}