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    }