001/**
002 * Logback: the reliable, generic, fast and flexible logging framework.
003 * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
004 *
005 * This program and the accompanying materials are dual-licensed under
006 * either the terms of the Eclipse Public License v1.0 as published by
007 * the Eclipse Foundation
008 *
009 *   or (per the licensee's choosing)
010 *
011 * under the terms of the GNU Lesser General Public License version 2.1
012 * as published by the Free Software Foundation.
013 */
014package ch.qos.logback.classic.pattern;
015
016import ch.qos.logback.classic.spi.ILoggingEvent;
017
018import java.util.Map;
019
020import static ch.qos.logback.core.util.OptionHelper.extractDefaultReplacement;
021
022public class MDCConverter extends ClassicConverter {
023
024    private String key;
025    private String defaultValue = "";
026
027    @Override
028    public void start() {
029        String[] keyInfo = extractDefaultReplacement(getFirstOption());
030        key = keyInfo[0];
031        if (keyInfo[1] != null) {
032            defaultValue = keyInfo[1];
033        }
034        super.start();
035    }
036
037    @Override
038    public void stop() {
039        key = null;
040        super.stop();
041    }
042
043    @Override
044    public String convert(ILoggingEvent event) {
045        Map<String, String> mdcPropertyMap = event.getMDCPropertyMap();
046
047        if (mdcPropertyMap == null) {
048            return defaultValue;
049        }
050
051        if (key == null) {
052            return outputMDCForAllKeys(mdcPropertyMap);
053        } else {
054
055            String value = mdcPropertyMap.get(key);
056            if (value != null) {
057                return value;
058            } else {
059                return defaultValue;
060            }
061        }
062    }
063
064    /**
065     * if no key is specified, return all the values present in the MDC, in the format "k1=v1, k2=v2, ..."
066     */
067    private String outputMDCForAllKeys(Map<String, String> mdcPropertyMap) {
068        StringBuilder buf = new StringBuilder();
069        boolean first = true;
070        for (Map.Entry<String, String> entry : mdcPropertyMap.entrySet()) {
071            if (first) {
072                first = false;
073            } else {
074                buf.append(", ");
075            }
076            // format: key0=value0, key1=value1
077            buf.append(entry.getKey()).append('=').append(entry.getValue());
078        }
079        return buf.toString();
080    }
081}