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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.appender.rewrite;
18  
19  import java.util.HashMap;
20  import java.util.Map;
21  
22  import org.apache.logging.log4j.Logger;
23  import org.apache.logging.log4j.core.LogEvent;
24  import org.apache.logging.log4j.core.config.plugins.Plugin;
25  import org.apache.logging.log4j.core.config.plugins.PluginAttribute;
26  import org.apache.logging.log4j.core.config.plugins.PluginElement;
27  import org.apache.logging.log4j.core.config.plugins.PluginFactory;
28  import org.apache.logging.log4j.core.impl.Log4jLogEvent;
29  import org.apache.logging.log4j.core.util.KeyValuePair;
30  import org.apache.logging.log4j.message.MapMessage;
31  import org.apache.logging.log4j.message.Message;
32  import org.apache.logging.log4j.status.StatusLogger;
33  
34  /**
35   * This policy modifies events by replacing or possibly adding keys and values to the MapMessage.
36   */
37  @Plugin(name = "MapRewritePolicy", category = "Core", elementType = "rewritePolicy", printObject = true)
38  public final class MapRewritePolicy implements RewritePolicy {
39      /**
40       * Allow subclasses access to the status logger without creating another instance.
41       */
42      protected static final Logger LOGGER = StatusLogger.getLogger();
43  
44      private final Map<String, String> map;
45  
46      private final Mode mode;
47  
48      private MapRewritePolicy(final Map<String, String> map, final Mode mode) {
49          this.map = map;
50          this.mode = mode;
51      }
52  
53      /**
54       * Rewrite the event.
55       * @param source a logging event that may be returned or
56       * used to create a new logging event.
57       * @return The LogEvent after rewriting.
58       */
59      @Override
60      public LogEvent rewrite(final LogEvent source) {
61          final Message msg = source.getMessage();
62          if (msg == null || !(msg instanceof MapMessage)) {
63              return source;
64          }
65  
66          final Map<String, String> newMap = new HashMap<>(((MapMessage) msg).getData());
67          switch (mode) {
68              case Add: {
69                  newMap.putAll(map);
70                  break;
71              }
72              default: {
73                  for (final Map.Entry<String, String> entry : map.entrySet()) {
74                      if (newMap.containsKey(entry.getKey())) {
75                          newMap.put(entry.getKey(), entry.getValue());
76                      }
77                  }
78              }
79          }
80          final MapMessage message = ((MapMessage) msg).newInstance(newMap);
81          final LogEvent result = new Log4jLogEvent.Builder(source).setMessage(message).build();
82          return result;
83      }
84  
85      /**
86       * An enumeration to identify whether keys not in the MapMessage should be added or whether only existing
87       * keys should be updated.
88       */
89      public enum Mode {
90          /**
91           * Keys should be added.
92           */
93          Add,
94          /**
95           * Keys should be updated.
96           */
97          Update
98      }
99  
100     @Override
101     public String toString() {
102         final StringBuilder sb = new StringBuilder();
103         sb.append("mode=").append(mode);
104         sb.append(" {");
105         boolean first = true;
106         for (final Map.Entry<String, String> entry : map.entrySet()) {
107             if (!first) {
108                 sb.append(", ");
109             }
110             sb.append(entry.getKey()).append('=').append(entry.getValue());
111             first = false;
112         }
113         sb.append('}');
114         return sb.toString();
115     }
116 
117     /**
118      * The factory method to create the MapRewritePolicy.
119      * @param mode The string representation of the Mode.
120      * @param pairs key/value pairs for the new Map keys and values.
121      * @return The MapRewritePolicy.
122      */
123     @PluginFactory
124     public static MapRewritePolicy createPolicy(
125             @PluginAttribute("mode") final String mode,
126             @PluginElement("KeyValuePair") final KeyValuePair[] pairs) {
127         Mode op = mode == null ? op = Mode.Add : Mode.valueOf(mode);
128         if (pairs == null || pairs.length == 0) {
129             LOGGER.error("keys and values must be specified for the MapRewritePolicy");
130             return null;
131         }
132         final Map<String, String> map = new HashMap<>();
133         for (final KeyValuePair pair : pairs) {
134             final String key = pair.getKey();
135             if (key == null) {
136                 LOGGER.error("A null key is not valid in MapRewritePolicy");
137                 continue;
138             }
139             final String value = pair.getValue();
140             if (value == null) {
141                 LOGGER.error("A null value for key " + key + " is not allowed in MapRewritePolicy");
142                 continue;
143             }
144             map.put(pair.getKey(), pair.getValue());
145         }
146         if (map.isEmpty()) {
147             LOGGER.error("MapRewritePolicy is not configured with any valid key value pairs");
148             return null;
149         }
150         return new MapRewritePolicy(map, op);
151     }
152 }