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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 java.util.Map;
import org.ops4j.pax.logging.PaxContext;
import org.ops4j.pax.logging.PaxLoggingManager;
import org.ops4j.pax.logging.PaxLoggingService;
/**
* 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 class MDC {
/** {@link PaxContext} used when {@link org.ops4j.pax.logging.PaxLoggingService} is not available */
private static PaxContext m_defaultContext = new PaxContext();
/** {@link PaxContext} obtained from {@link org.ops4j.pax.logging.PaxLoggingService} */
private static PaxContext m_context;
private MDC() {
}
/**
*
For all the methods that use the context, default, static, {@link PaxContext} may be used (tied to pax-logging-api
* bundle) if there's no available {@link PaxLoggingManager} or {@link PaxLoggingService}. If the service is
* available, it is always used to get service specific {@link PaxContext}.
* Refering always to {@link PaxLoggingService#getPaxContext()} is cheap operation, as it's
* only reference to fields.
*
* See: https://ops4j1.jira.com/browse/PAXLOGGING-247
*
* @return m_context if the MDC should use the PaxContext object from the PaxLoggingManager,
* or m_defaultContext if the logging manager is not set, or does not have its context available yet.
*/
private static PaxContext getPaxContext() {
PaxLoggingManager manager = Logger.m_paxLogging;
if (manager != null) {
synchronized (MDC.class) {
PaxLoggingService service = manager.getPaxLoggingService();
m_context = service != null ? service.getPaxContext() : null;
}
}
return m_context != null ? m_context : m_defaultContext;
}
/**
* Put a context value (the o parameter) as identified with the
* 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.
*/
static public void put(String key, Object o) {
getPaxContext().put(key, o);
}
/**
* Get the context identified by the key parameter.
*
*
* This method has no side effects.
*/
static public Object get(String key) {
return getPaxContext().get(key);
}
/**
* Remove the the context identified by the key parameter.
*/
static public void remove(String key) {
getPaxContext().remove(key);
}
/**
* Get the current thread's MDC as a hashtable. This method is intended to be used internally.
*
* pax-logging note: this method has different return type than original {@code org.apache.log4j.MDC}.
* Originally this method returns {@link Hashtable}, but pax-logging's version
* returned {@link Map} for very long time.
*/
public static Map getContext() {
return getPaxContext().getContext();
}
/**
* Remove all values from the MDC.
*
* @since 1.2.16
*/
public static void clear() {
getPaxContext().clear();
}
}