org.apache.log4j.MDC 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.log4j;
import java.util.Hashtable;
import org.apache.log4j.helpers.ThreadLocalMap;
/**
* 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.
*
* @since 1.2
*
* @author Ceki Gülcü
*/
public class MDC {
final static MDC mdc = new MDC();
static final int HT_SIZE = 7;
// boolean java1;
ThreadLocalMap tlm;
private MDC() {
tlm = new ThreadLocalMap();
}
/**
* 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) {
if (mdc != null) {
mdc.put0(key, o);
}
}
/**
* Get the context identified by the key parameter.
*
*
* This method has no side effects.
*/
static public Object get(String key) {
if (mdc != null) {
return mdc.get0(key);
}
return null;
}
/**
* Remove the the context identified by the key parameter.
*
*/
static public void remove(String key) {
if (mdc != null) {
mdc.remove0(key);
}
}
/**
* Get the current thread's MDC as a hashtable. This method is intended to be
* used internally.
*/
public static Hashtable getContext() {
if (mdc != null) {
return mdc.getContext0();
} else {
return null;
}
}
/**
* Remove all values from the MDC.
*
* @since 1.2.16
*/
public static void clear() {
if (mdc != null) {
mdc.clear0();
}
}
private void put0(String key, Object o) {
if (tlm == null) {
return;
} else {
Hashtable ht = (Hashtable) ((ThreadLocalMap) tlm).get();
if (ht == null) {
ht = new Hashtable(HT_SIZE);
((ThreadLocalMap) tlm).set(ht);
}
ht.put(key, o);
}
}
private Object get0(String key) {
if (tlm == null) {
return null;
} else {
Hashtable ht = (Hashtable) ((ThreadLocalMap) tlm).get();
if (ht != null && key != null) {
return ht.get(key);
} else {
return null;
}
}
}
private void remove0(String key) {
if (tlm != null) {
Hashtable ht = (Hashtable) ((ThreadLocalMap) tlm).get();
if (ht != null) {
ht.remove(key);
// clean up if this was the last key
if (ht.isEmpty()) {
clear0();
}
}
}
}
private Hashtable getContext0() {
if (tlm == null) {
return null;
} else {
return (Hashtable) ((ThreadLocalMap) tlm).get();
}
}
private void clear0() {
if (tlm != null) {
Hashtable ht = (Hashtable) ((ThreadLocalMap) tlm).get();
if (ht != null) {
ht.clear();
}
tlm.remove();
}
}
}