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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.Map;
20  
21  import org.apache.logging.log4j.core.LogEvent;
22  import org.apache.logging.log4j.core.config.plugins.Plugin;
23  import org.apache.logging.log4j.message.MapMessage;
24  
25  /**
26   * The basis for a lookup based on a Map.
27   */
28  @Plugin(name = "map", category = "Lookup")
29  public class MapLookup implements StrLookup {
30      /**
31       * Map keys are variable names and value.
32       */
33      private final Map<String, String> map;
34  
35      /**
36       * Creates a new instance backed by a Map. Used by the default lookup.
37       *
38       * @param map the map of keys to values, may be null
39       */
40      public MapLookup(final Map<String, String> map) {
41          this.map = map;
42      }
43  
44      /**
45       * Constructor when used directly as a plugin.
46       */
47      public MapLookup() {
48          this.map = null;
49      }
50  
51      /**
52       * Looks up a String key to a String value using the map.
53       * <p/>
54       * If the map is null, then null is returned.
55       * The map result object is converted to a string using toString().
56       *
57       * @param key the key to be looked up, may be null
58       * @return the matching value, null if no match
59       */
60      @Override
61      public String lookup(final String key) {
62          if (map == null) {
63              return null;
64          }
65          final String obj = map.get(key);
66          if (obj == null) {
67              return null;
68          }
69          return obj;
70      }
71  
72      @Override
73      public String lookup(final LogEvent event, final String key) {
74          if (map == null && !(event.getMessage() instanceof MapMessage)) {
75              return null;
76          }
77          if (map != null && map.containsKey(key)) {
78              final String obj = map.get(key);
79              if (obj != null) {
80                  return obj;
81              }
82          }
83          if (event.getMessage() instanceof MapMessage) {
84              return ((MapMessage) event.getMessage()).get(key);
85          }
86          return null;
87      }
88  }