001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache license, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the license for the specific language governing permissions and
015 * limitations under the license.
016 */
017package org.apache.logging.log4j.core.pattern;
018
019import java.util.Map;
020import java.util.Set;
021import java.util.TreeSet;
022
023import org.apache.logging.log4j.core.LogEvent;
024import org.apache.logging.log4j.core.config.plugins.Plugin;
025
026/**
027 * Able to handle the contents of the LogEvent's MDC and either
028 * output the entire contents of the properties in a similar format to the
029 * java.util.Hashtable.toString(), or to output the value of a specific key
030 * within the property bundle
031 * when this pattern converter has the option set.
032 */
033 @Plugin(name = "MdcPatternConverter", category = PatternConverter.CATEGORY)
034@ConverterKeys({ "X", "mdc", "MDC" })
035public final class MdcPatternConverter extends LogEventPatternConverter {
036    /**
037     * Name of property to output.
038     */
039    private final String key;
040
041    /**
042     * Private constructor.
043     *
044     * @param options options, may be null.
045     */
046    private MdcPatternConverter(final String[] options) {
047        super(options != null && options.length > 0 ? "MDC{" + options[0] + '}' : "MDC", "mdc");
048        key = options != null && options.length > 0 ? options[0] : null;
049    }
050
051    /**
052     * Obtains an instance of PropertiesPatternConverter.
053     *
054     * @param options options, may be null or first element contains name of property to format.
055     * @return instance of PropertiesPatternConverter.
056     */
057    public static MdcPatternConverter newInstance(final String[] options) {
058        return new MdcPatternConverter(options);
059    }
060
061    /**
062     * {@inheritDoc}
063     */
064    @Override
065    public void format(final LogEvent event, final StringBuilder toAppendTo) {
066        final Map<String, String> contextMap = event.getContextMap();
067        // if there is no additional options, we output every single
068        // Key/Value pair for the MDC in a similar format to Hashtable.toString()
069        if (key == null) {
070
071
072            if (contextMap == null || contextMap.isEmpty()) {
073                toAppendTo.append("{}");
074                return;
075            }
076            final StringBuilder sb = new StringBuilder("{");
077            final Set<String> keys = new TreeSet<String>(contextMap.keySet());
078            for (final String key : keys) {
079                if (sb.length() > 1) {
080                    sb.append(", ");
081                }
082                sb.append(key).append('=').append(contextMap.get(key));
083
084            }
085            sb.append('}');
086            toAppendTo.append(sb);
087        } else if (contextMap != null) {
088            // otherwise they just want a single key output
089            final Object val = contextMap.get(key);
090
091            if (val != null) {
092                toAppendTo.append(val);
093            }
094        }
095    }
096}