Logback: the reliable, generic, fast and flexible logging framework.
Copyright (C) 1999-2015, QOS.ch. All rights reserved.
This program and the accompanying materials are dual-licensed under
either the terms of the Eclipse Public License v1.0 as published by
the Eclipse Foundation
  or (per the licensee's choosing)
under the terms of the GNU Lesser General Public License version 2.1
as published by the Free Software Foundation.
/**
 * Logback: the reliable, generic, fast and flexible logging framework.
 * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
 *
 * This program and the accompanying materials are dual-licensed under
 * either the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation
 *
 *   or (per the licensee's choosing)
 *
 * under the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation.
 */
package ch.qos.logback.classic.pattern;

import ch.qos.logback.classic.spi.ILoggingEvent;

import java.util.Map;

import static ch.qos.logback.core.util.OptionHelper.extractDefaultReplacement;

public class MDCConverter extends ClassicConverter {

    private String key;
    private String defaultValue = "";

    @Override
    public void start() {
        String[] keyInfo = extractDefaultReplacement(getFirstOption());
        key = keyInfo[0];
        if (keyInfo[1] != null) {
            defaultValue = keyInfo[1];
        }
        super.start();
    }

    @Override
    public void stop() {
        key = null;
        super.stop();
    }

    @Override
    public String convert(ILoggingEvent event) {
        Map<String, String> mdcPropertyMap = event.getMDCPropertyMap();

        if (mdcPropertyMap == null) {
            return defaultValue;
        }

        if (key == null) {
            return outputMDCForAllKeys(mdcPropertyMap);
        } else {

            String value = mdcPropertyMap.get(key);
            if (value != null) {
                return value;
            } else {
                return defaultValue;
            }
        }
    }

    
if no key is specified, return all the values present in the MDC, in the format "k1=v1, k2=v2, ..."
/**
     * if no key is specified, return all the values present in the MDC, in the format "k1=v1, k2=v2, ..."
     */
    private String outputMDCForAllKeys(Map<String, String> mdcPropertyMap) {
        StringBuilder buf = new StringBuilder();
        boolean first = true;
        for (Map.Entry<String, String> entry : mdcPropertyMap.entrySet()) {
            if (first) {
                first = false;
            } else {
                buf.append(", ");
            }
            // format: key0=value0, key1=value1
            buf.append(entry.getKey()).append('=').append(entry.getValue());
        }
        return buf.toString();
    }
}