org.apache.log4j: public class: MDC

org.apache.log4j
public class: MDC [javadoc | source]

java.lang.Object
   org.apache.log4j.MDC

The MDC class is similar to the 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

Field Summary
static final MDC	mdc
static final int	HT_SIZE
boolean	java1
Object	tlm

Method from org.apache.log4j.MDC Summary:
clear, get, getContext, put, remove

Methods from java.lang.Object:
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method from org.apache.log4j.MDC Detail:
public static void clear() { if (mdc != null) { mdc.clear0(); } } Remove all values from the MDC.
public static Object get(String key) { if (mdc != null) { return mdc.get0(key); } return null; } Get the context identified by the `key` parameter. This method has no side effects.
public static Hashtable getContext() { if (mdc != null) { return mdc.getContext0(); } else { return null; } } Get the current thread's MDC as a hashtable. This method is intended to be used internally.
public static void put(String key, Object o) { if (mdc != null) { mdc.put0(key, o); } } 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.
public static void remove(String key) { if (mdc != null) { mdc.remove0(key); } } Remove the the context identified by the `key` parameter.

Method from org.apache.log4j.MDC Detail:

 public static  void clear() {
    if (mdc != null) {
        mdc.clear0();
    }
}

Remove all values from the MDC.

 public static Object get(String key) {
    if (mdc != null) {
        return mdc.get0(key);
    }
    return null;
}

key

This method has no side effects.

 public static Hashtable getContext() {
    if (mdc != null) {
        return mdc.getContext0();
    } else {
        return null;
    }
}

Get the current thread's MDC as a hashtable. This method is intended to be used internally.

 public static  void put(String key,
    Object o) {
     if (mdc != null) {
         mdc.put0(key, o);
     }
}

o

key

If the current thread does not have a context map it is created as a side effect.

 public static  void remove(String key) {
    if (mdc != null) {
        mdc.remove0(key);
    }
}

key