/**
* Copyright (c) 2004-2011 QOS.ch
* All rights reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
*/
package org.slf4j;
import java.io.Closeable;
import java.util.Map;
import org.slf4j.helpers.NOPMDCAdapter;
import org.slf4j.helpers.BasicMDCAdapter;
import org.slf4j.helpers.Util;
import org.slf4j.impl.StaticMDCBinder;
import org.slf4j.spi.MDCAdapter;
/**
* This class hides and serves as a substitute for the underlying logging
* system's MDC implementation.
*
* <p>
* If the underlying logging system offers MDC functionality, then SLF4J's MDC,
* i.e. this class, will delegate to the underlying system's MDC. Note that at
* this time, only two logging systems, namely log4j and logback, offer MDC
* functionality. For java.util.logging which does not support MDC,
* {@link BasicMDCAdapter} will be used. For other systems, i.e slf4j-simple
* and slf4j-nop, {@link NOPMDCAdapter} will be used.
*
* <p>
* Thus, as a SLF4J user, you can take advantage of MDC in the presence of log4j,
* logback, or java.util.logging, but without forcing these systems as
* dependencies upon your users.
*
* <p>
* For more information on MDC please see the <a
* href="http://logback.qos.ch/manual/mdc.html">chapter on MDC</a> in the
* logback manual.
*
* <p>
* Please note that all methods in this class are static.
*
* @author Ceki Gülcü
* @since 1.4.1
*/
public class MDC {
static final String NULL_MDCA_URL = "http://www.slf4j.org/codes.html#null_MDCA";
static final String NO_STATIC_MDC_BINDER_URL = "http://www.slf4j.org/codes.html#no_static_mdc_binder";
static MDCAdapter mdcAdapter;
/**
* An adapter to remove the key when done.
*/
public static class MDCCloseable implements Closeable {
private final String key;
private MDCCloseable(String key) {
this.key = key;
}
public void close() {
MDC.remove(this.key);
}
}
private MDC() {
}
/**
* As of SLF4J version 1.7.14, StaticMDCBinder classes shipping in various bindings
* come with a getSingleton() method. Previously only a public field called SINGLETON
* was available.
*
* @return MDCAdapter
* @throws NoClassDefFoundError in case no binding is available
* @since 1.7.14
*/
private static MDCAdapter bwCompatibleGetMDCAdapterFromBinder() throws NoClassDefFoundError {
try {
return StaticMDCBinder.getSingleton().getMDCA();
} catch (NoSuchMethodError nsme) {
// binding is probably a version of SLF4J older than 1.7.14
return StaticMDCBinder.SINGLETON.getMDCA();
}
}
static {
try {
mdcAdapter = bwCompatibleGetMDCAdapterFromBinder();
} catch (NoClassDefFoundError ncde) {
mdcAdapter = new NOPMDCAdapter();
String msg = ncde.getMessage();
if (msg != null && msg.contains("StaticMDCBinder")) {
Util.report("Failed to load class \"org.slf4j.impl.StaticMDCBinder\".");
Util.report("Defaulting to no-operation MDCAdapter implementation.");
Util.report("See " + NO_STATIC_MDC_BINDER_URL + " for further details.");
} else {
throw ncde;
}
} catch (Exception e) {
// we should never get here
Util.report("MDC binding unsuccessful.", e);
}
}
/**
* Put a diagnostic context value (the <code>val</code> parameter) as identified with the
* <code>key</code> parameter into the current thread's diagnostic context map. The
* <code>key</code> parameter cannot be null. The <code>val</code> parameter
* can be null only if the underlying implementation supports it.
*
* <p>
* This method delegates all work to the MDC of the underlying logging system.
*
* @param key non-null key
* @param val value to put in the map
*
* @throws IllegalArgumentException
* in case the "key" parameter is null
*/
public static void put(String key, String val) throws IllegalArgumentException {
if (key == null) {
throw new IllegalArgumentException("key parameter cannot be null");
}
if (mdcAdapter == null) {
throw new IllegalStateException("MDCAdapter cannot be null. See also " + NULL_MDCA_URL);
}
mdcAdapter.put(key, val);
}
/**
* Put a diagnostic context value (the <code>val</code> parameter) as identified with the
* <code>key</code> parameter into the current thread's diagnostic context map. The
* <code>key</code> parameter cannot be null. The <code>val</code> parameter
* can be null only if the underlying implementation supports it.
*
* <p>
* This method delegates all work to the MDC of the underlying logging system.
* <p>
* This method return a <code>Closeable</code> object who can remove <code>key</code> when
* <code>close</code> is called.
*
* <p>
* Useful with Java 7 for example :
* <code>
* try(MDC.MDCCloseable closeable = MDC.putCloseable(key, value)) {
* ....
* }
* </code>
*
* @param key non-null key
* @param val value to put in the map
* @return a <code>Closeable</code> who can remove <code>key</code> when <code>close</code>
* is called.
*
* @throws IllegalArgumentException
* in case the "key" parameter is null
*/
public static MDCCloseable putCloseable(String key, String val) throws IllegalArgumentException {
put(key, val);
return new MDCCloseable(key);
}
/**
* Get the diagnostic context identified by the <code>key</code> parameter. The
* <code>key</code> parameter cannot be null.
*
* <p>
* This method delegates all work to the MDC of the underlying logging system.
*
* @param key
* @return the string value identified by the <code>key</code> parameter.
* @throws IllegalArgumentException
* in case the "key" parameter is null
*/
public static String get(String key) throws IllegalArgumentException {
if (key == null) {
throw new IllegalArgumentException("key parameter cannot be null");
}
if (mdcAdapter == null) {
throw new IllegalStateException("MDCAdapter cannot be null. See also " + NULL_MDCA_URL);
}
return mdcAdapter.get(key);
}
/**
* Remove the diagnostic context identified by the <code>key</code> parameter using
* the underlying system's MDC implementation. The <code>key</code> parameter
* cannot be null. This method does nothing if there is no previous value
* associated with <code>key</code>.
*
* @param key
* @throws IllegalArgumentException
* in case the "key" parameter is null
*/
public static void remove(String key) throws IllegalArgumentException {
if (key == null) {
throw new IllegalArgumentException("key parameter cannot be null");
}
if (mdcAdapter == null) {
throw new IllegalStateException("MDCAdapter cannot be null. See also " + NULL_MDCA_URL);
}
mdcAdapter.remove(key);
}
/**
* Clear all entries in the MDC of the underlying implementation.
*/
public static void clear() {
if (mdcAdapter == null) {
throw new IllegalStateException("MDCAdapter cannot be null. See also " + NULL_MDCA_URL);
}
mdcAdapter.clear();
}
/**
* Return a copy of the current thread's context map, with keys and values of
* type String. Returned value may be null.
*
* @return A copy of the current thread's context map. May be null.
* @since 1.5.1
*/
public static Map<String, String> getCopyOfContextMap() {
if (mdcAdapter == null) {
throw new IllegalStateException("MDCAdapter cannot be null. See also " + NULL_MDCA_URL);
}
return mdcAdapter.getCopyOfContextMap();
}
/**
* Set the current thread's context map by first clearing any existing map and
* then copying the map passed as parameter. The context map passed as
* parameter must only contain keys and values of type String.
*
* @param contextMap
* must contain only keys and values of type String
* @since 1.5.1
*/
public static void setContextMap(Map<String, String> contextMap) {
if (mdcAdapter == null) {
throw new IllegalStateException("MDCAdapter cannot be null. See also " + NULL_MDCA_URL);
}
mdcAdapter.setContextMap(contextMap);
}
/**
* Returns the MDCAdapter instance currently in use.
*
* @return the MDcAdapter instance currently in use.
* @since 1.4.2
*/
public static MDCAdapter getMDCAdapter() {
return mdcAdapter;
}
}