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.lookup;
018
019import java.util.HashMap;
020import java.util.List;
021import java.util.Map;
022
023import org.apache.logging.log4j.core.LogEvent;
024import org.apache.logging.log4j.core.config.plugins.Plugin;
025import org.apache.logging.log4j.message.MapMessage;
026
027/**
028 * A map-based lookup.
029 */
030@Plugin(name = "map", category = StrLookup.CATEGORY)
031public 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}