org.apache.log4j
Class MDC

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

public class MDC

extends Object

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

put

public static void put(String key,
                       Object 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.

get

public static Object get(String key)

Get the context identified by the key parameter.

This method has no side effects.

remove

public static void remove(String key)

Remove the the context identified by the key parameter.

getContext

public static Hashtable getContext()

Get the current thread's MDC as a hashtable.