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    1   /*
    2    * Licensed to the Apache Software Foundation (ASF) under one or more
    3    * contributor license agreements. See the NOTICE file distributed with
    4    * this work for additional information regarding copyright ownership.
    5    * The ASF licenses this file to You under the Apache license, Version 2.0
    6    * (the "License"); you may not use this file except in compliance with
    7    * the License. You may obtain a copy of the License at
    8    *
    9    *      http://www.apache.org/licenses/LICENSE-2.0
    10   *
    11   * Unless required by applicable law or agreed to in writing, software
    12   * distributed under the License is distributed on an "AS IS" BASIS,
    13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    14   * See the license for the specific language governing permissions and
    15   * limitations under the license.
    16   */
    17  package org.apache.logging.log4j.core.lookup;
    18
    19  import java.util.HashMap;
    20  import java.util.List;
    21  import java.util.Map;
    22
    23  import org.apache.logging.log4j.core.LogEvent;
    24  import org.apache.logging.log4j.core.config.plugins.Plugin;
    25  import org.apache.logging.log4j.message.MapMessage;
    26
    27  /**
    28   * A map-based lookup.
    29   */
    30  @Plugin(name = "map", category = StrLookup.CATEGORY)
    31  public class MapLookup implements StrLookup {
    32
    33      /**
    34       * A singleton used by a main method to save its arguments.
    35       */
    36      static final MapLookup MAIN_SINGLETON = new MapLookup(newMap(0));
    37
    38      static Map<String, String> initMap(final String[] srcArgs, final Map<String, String> destMap) {
    39          for (int i = 0; i < srcArgs.length; i++) {
    40              final int next = i + 1;
    41              final String value = srcArgs[i];
    42              destMap.put(Integer.toString(i), value);
    43              destMap.put(value, next < srcArgs.length ? srcArgs[next] : null);
    44          }
    45          return destMap;
    46      }
    47
    48      private static HashMap<String, String> newMap(final int initialCapacity) {
    49          return new HashMap<String, String>(initialCapacity);
    50      }
    51
    52      /**
    53       * An application's {@code public static main(String[])} method calls this method to make its main arguments
    54       * available for lookup with the prefix {@code main}.
    55       * <p>
    56       * The map provides two kinds of access: First by index, starting at {@code "0"}, {@code "1"} and so on. For
    57       * example, the command line {@code --file path/file.txt -x 2} can be accessed from a configuration file with:
    58       * </p>
    59       * <ul>
    60       * <li>{@code "main:0"} = {@code "--file"}</li>
    61       * <li>{@code "main:1"} = {@code "path/file.txt"}</li>
    62       * <li>{@code "main:2"} = {@code "-x"}</li>
    63       * <li>{@code "main:3"} = {@code "2"}</li>
    64       * </ul>
    65       * <p>
    66       * Second using the argument at position n as the key to access the value at n+1.
    67       * </p>
    68       * <ul>
    69       * <li>{@code "main:--file"} = {@code "path/file.txt"}</li>
    70       * <li>{@code "main:-x"} = {@code "2"}</li>
    71       * </ul>
    72       *
    73       * @param args
    74       *        An application's {@code public static main(String[])} arguments.
    75       * @since 2.1
    76       */
    77      public static void setMainArguments(final String[] args) {
    78          if (args == null) {
    79              return;
    80          }
    81          initMap(args, MAIN_SINGLETON.map);
    82      }
    83
    84      static Map<String, String> toMap(final List<String> args) {
    85          if (args == null) {
    86              return null;
    87          }
    88          final int size = args.size();
    89          return initMap(args.toArray(new String[size]), newMap(size));
    90      }
    91
    92      static Map<String, String> toMap(final String[] args) {
    93          if (args == null) {
    94              return null;
    95          }
    96          return initMap(args, newMap(args.length));
    97      }
    98
    99      /**
    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 }