org.slf4j/slf4j-api/1.7.25 : org/slf4j/MDC.java

http://www.slf4j.org: The slf4j API (QOS.ch)
MIT License
Ceki Gulcu
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.
/**
 * 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.
 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, BasicMDCAdapter will be used. For other systems, i.e. slf4j-simple and slf4j-nop, NOPMDCAdapter will be used. 

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.

For more information on MDC please see the chapter on MDC in the
logback manual.

Please note that all methods in this class are static.
Author: Ceki Gülcü
Since: 1.4.1/**
 * 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 G&uuml;lc&uuml;
 * @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.
/**
     * 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.
Throws: NoClassDefFoundError – in case no binding is available
Returns: MDCAdapter
Since: 1.7.14/**
     * 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 val parameter) as identified with the
key parameter into the current thread's diagnostic context map. The
key parameter cannot be null. The val parameter
can be null only if the underlying implementation supports it.

This method delegates all work to the MDC of the underlying logging system.
Params: key – non-null key
val – value to put in the map
Throws: IllegalArgumentException – 
          in case the "key" parameter is null/**
     * 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 val parameter) as identified with the
key parameter into the current thread's diagnostic context map. The
key parameter cannot be null. The val parameter
can be null only if the underlying implementation supports it.

This method delegates all work to the MDC of the underlying logging system.

This method return a Closeable object who can remove key when
close is called.

Useful with Java 7 for example :

  try(MDC.MDCCloseable closeable = MDC.putCloseable(key, value)) {
    ....
  }

Params: key – non-null key
val – value to put in the map
Throws: IllegalArgumentException – 
          in case the "key" parameter is null
Returns: a Closeable who can remove key when close
is called./**
     * 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 key parameter. The
key parameter cannot be null.

This method delegates all work to the MDC of the underlying logging system.
Params: key – 
Throws: IllegalArgumentException – 
          in case the "key" parameter is null
Returns: the string value identified by the key parameter./**
     * 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 key parameter using
the underlying system's MDC implementation. The key parameter
cannot be null. This method does nothing if there is no previous value
associated with key.
Params: key – 
Throws: IllegalArgumentException – 
          in case the "key" parameter is null/**
     * 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.
/**
     * 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.
Returns: A copy of the current thread's context map. May be null.
Since: 1.5.1/**
     * 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.
Params: contextMap – 
         must contain only keys and values of type String
Since: 1.5.1/**
     * 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.
Returns: the MDcAdapter instance currently in use.
Since: 1.4.2/**
     * Returns the MDCAdapter instance currently in use.
     * 
     * @return the MDcAdapter instance currently in use.
     * @since 1.4.2
     */
    public static MDCAdapter getMDCAdapter() {
        return mdcAdapter;
    }

}
Throws:	NoClassDefFoundError – in case no binding is available
Returns:	MDCAdapter
Since:	1.7.14
Params:	key – non-null key val – value to put in the map
Throws:	IllegalArgumentException – in case the "key" parameter is null
Params:	key –
Throws:	IllegalArgumentException – in case the "key" parameter is null
Returns:	the string value identified by the `key` parameter.
Returns:	A copy of the current thread's context map. May be null.
Since:	1.5.1
Params:	contextMap – must contain only keys and values of type String
Since:	1.5.1
Returns:	the MDcAdapter instance currently in use.
Since:	1.4.2
/

org.slf4j/ slf4j-api/ 1.7.25/ org/slf4j/MDC.java
