rgoers/log4j2-core/src/main/java/org/apache/logging/log4j/core/pattern/MapPatternConverter.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache license, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the license for the specific language governing permissions and
 * limitations under the license.
 */
package org.apache.logging.log4j.core.pattern;

import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.config.plugins.Plugin;
import org.apache.logging.log4j.message.MapMessage;

import java.util.Map;
import java.util.Set;
import java.util.TreeSet;

/**
 * Able to handle the contents of the LogEvent's MapMessage and either
 * output the entire contents of the properties in a similar format to the
 * java.util.Hashtable.toString(), or to output the value of a specific key
 * within the Map.
 */
@Plugin(name = "MapPatternConverter", type = "Converter")
@ConverterKeys({"K", "map", "MAP" })
public final class MapPatternConverter extends LogEventPatternConverter {
    /**
     * Name of property to output.
     */
    private final String key;

    /**
     * Private constructor.
     *
     * @param options options, may be null.
     */
    private MapPatternConverter(final String[] options) {
        super(((options != null) && (options.length > 0)) ? ("MAP{" + options[0] + "}") : "MAP", "map");
        key = (options != null && options.length > 0) ? options[0] : null;
    }

    /**
     * Obtains an instance of PropertiesPatternConverter.
     *
     * @param options options, may be null or first element contains name of property to format.
     * @return instance of PropertiesPatternConverter.
     */
    public static MapPatternConverter newInstance(final String[] options) {
        return new MapPatternConverter(options);
    }

    /**
     * {@inheritDoc}
     */
    public void format(final LogEvent event, final StringBuilder toAppendTo) {
        MapMessage msg;
        if (event.getMessage() instanceof MapMessage) {
            msg = (MapMessage) event.getMessage();
        } else {
            return;
        }
        Map<String, String> map = msg.getData();
        // if there is no additional options, we output every single
        // Key/Value pair for the Map in a similar format to Hashtable.toString()
        if (key == null) {
            if (map.size() == 0) {
                toAppendTo.append("{}");
                return;
            }
            StringBuilder sb = new StringBuilder("{");
            Set<String> keys = new TreeSet<String>(map.keySet());
            for (String key : keys) {
                if (sb.length() > 1) {
                    sb.append(", ");
                }
                sb.append(key).append("=").append(map.get(key));

            }
            sb.append("}");
            toAppendTo.append(sb);
        } else {
            // otherwise they just want a single key output
            String val = map.get(key);

            if (val != null) {
                toAppendTo.append(val);
            }
        }
    }
}