/*
* Copyright (C) The Apache Software Foundation. All rights reserved.
*
* This software is published under the terms of the Apache Software License
* version 1.1, a copy of which has been included with this distribution in
* the LICENSE.txt file.
*/
package org.apache.log4j;
import java.util.Hashtable;
import org.apache.log4j.helpers.Loader;
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 <em>mapped
diagnostic contexts</em>. A <em>Mapped Diagnostic Context</em>, 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.
<p><b><em>The MDC is managed on a per thread basis</em></b>. A
child thread automatically inherits a <em>copy</em> of the mapped
diagnostic context of its parent.
<p>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;
Object tlm;
private
MDC() {
java1 = Loader.isJava1();
if(!java1) {
tlm = new ThreadLocalMap();
}
}
/**
Put a context value (the <code>o</code> parameter) as identified
with the <code>key</code> parameter into the current thread's
context map.
<p>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) {
mdc.put0(key, o);
}
/**
Get the context identified by the <code>key</code> parameter.
<p>This method has no side effects.
*/
static
public
Object get(String key) {
return mdc.get0(key);
}
/**
Remove the the context identified by the <code>key</code>
parameter.
*/
static
public
void remove(String key) {
mdc.remove0(key);
}
/**
* Get the current thread's MDC as a hashtable. This method is
* intended to be used internally.
* */
public static Hashtable getContext() {
return mdc.getContext0();
}
private
void put0(String key, Object o) {
if(java1) {
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(java1) {
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(!java1) {
Hashtable ht = (Hashtable) ((ThreadLocalMap)tlm).get();
if(ht != null) {
ht.remove(key);
}
}
}
private
Hashtable getContext0() {
if(java1) {
return null;
} else {
return (Hashtable) ((ThreadLocalMap)tlm).get();
}
}
}
|