    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     */
    017    package org.apache.logging.log4j.core.lookup;
    018
    019    import java.util.HashMap;
    020    import java.util.List;
    021    import java.util.Map;
    022
    023    import org.apache.logging.log4j.core.LogEvent;
    024    import org.apache.logging.log4j.core.config.plugins.Plugin;
    025    import org.apache.logging.log4j.message.MapMessage;
    026
    027    /**
    028     * A map-based lookup.
    029     */
    030    @Plugin(name = "map", category = StrLookup.CATEGORY)
    031    public class MapLookup implements StrLookup {
    032
    033        /**
    034         * A singleton used by a main method to save its arguments.
    035         */
    036        static final MapLookup MAIN_SINGLETON = new MapLookup(newMap(0));
    037
    038        static Map<String, String> initMap(final String[] srcArgs, final Map<String, String> destMap) {
    039            for (int i = 0; i < srcArgs.length; i++) {
    040                final int next = i + 1;
    041                final String value = srcArgs[i];
    042                destMap.put(Integer.toString(i), value);
    043                destMap.put(value, next < srcArgs.length ? srcArgs[next] : null);
    044            }
    045            return destMap;
    046        }
    047
    048        private static HashMap<String, String> newMap(final int initialCapacity) {
    049            return new HashMap<String, String>(initialCapacity);
    050        }
    051
    052        /**
    053         * An application's {@code public static main(String[])} method calls this method to make its main arguments
    054         * available for lookup with the prefix {@code main}.
    055         * <p>
    056         * The map provides two kinds of access: First by index, starting at {@code "0"}, {@code "1"} and so on. For
    057         * example, the command line {@code --file path/file.txt -x 2} can be accessed from a configuration file with:
    058         * </p>
    059         * <ul>
    060         * <li>{@code "main:0"} = {@code "--file"}</li>
    061         * <li>{@code "main:1"} = {@code "path/file.txt"}</li>
    062         * <li>{@code "main:2"} = {@code "-x"}</li>
    063         * <li>{@code "main:3"} = {@code "2"}</li>
    064         * </ul>
    065         * <p>
    066         * Second using the argument at position n as the key to access the value at n+1.
    067         * </p>
    068         * <ul>
    069         * <li>{@code "main:--file"} = {@code "path/file.txt"}</li>
    070         * <li>{@code "main:-x"} = {@code "2"}</li>
    071         * </ul>
    072         *
    073         * @param args
    074         *        An application's {@code public static main(String[])} arguments.
    075         * @since 2.1
    076         */
    077        public static void setMainArguments(final String[] args) {
    078            if (args == null) {
    079                return;
    080            }
    081            initMap(args, MAIN_SINGLETON.map);
    082        }
    083
    084        static Map<String, String> toMap(final List<String> args) {
    085            if (args == null) {
    086                return null;
    087            }
    088            final int size = args.size();
    089            return initMap(args.toArray(new String[size]), newMap(size));
    090        }
    091
    092        static Map<String, String> toMap(final String[] args) {
    093            if (args == null) {
    094                return null;
    095            }
    096            return initMap(args, newMap(args.length));
    097        }
    098
    099        /**
    100         * Map keys are variable names and value.
    101         */
    102        private final Map<String, String> map;
    103
    104        /**
    105         * Constructor when used directly as a plugin.
    106         */
    107        public MapLookup() {
    108            this.map = null;
    109        }
    110
    111        /**
    112         * Creates a new instance backed by a Map. Used by the default lookup.
    113         *
    114         * @param map
    115         *        the map of keys to values, may be null
    116         */
    117        public MapLookup(final Map<String, String> map) {
    118            this.map = map;
    119        }
    120
    121        @Override
    122        public String lookup(final LogEvent event, final String key) {
    123            if (map == null && !(event.getMessage() instanceof MapMessage)) {
    124                return null;
    125            }
    126            if (map != null && map.containsKey(key)) {
    127                final String obj = map.get(key);
    128                if (obj != null) {
    129                    return obj;
    130                }
    131            }
    132            if (event.getMessage() instanceof MapMessage) {
    133                return ((MapMessage) event.getMessage()).get(key);
    134            }
    135            return null;
    136        }
    137
    138        /**
    139         * Looks up a String key to a String value using the map.
    140         * <p>
    141         * If the map is null, then null is returned. The map result object is converted to a string using toString().
    142         * </p>
    143         *
    144         * @param key
    145         *        the key to be looked up, may be null
    146         * @return the matching value, null if no match
    147         */
    148        @Override
    149        public String lookup(final String key) {
    150            if (map == null) {
    151                return null;
    152            }
    153            return map.get(key);
    154        }
    155
    156    }