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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.pattern;
18  
19  import java.util.Map;
20  import java.util.Set;
21  import java.util.TreeSet;
22  
23  import org.apache.logging.log4j.core.LogEvent;
24  import org.apache.logging.log4j.core.config.plugins.Plugin;
25  
26  /**
27   * Able to handle the contents of the LogEvent's MDC and either
28   * output the entire contents of the properties in a similar format to the
29   * java.util.Hashtable.toString(), or to output the value of a specific key
30   * within the property bundle
31   * when this pattern converter has the option set.
32   */
33   @Plugin(name = "MDCPatternConverter", category = "Converter")
34  @ConverterKeys({"X", "mdc", "MDC" })
35  public final class MDCPatternConverter extends LogEventPatternConverter {
36      /**
37       * Name of property to output.
38       */
39      private final String key;
40  
41      /**
42       * Private constructor.
43       *
44       * @param options options, may be null.
45       */
46      private MDCPatternConverter(final String[] options) {
47          super(options != null && options.length > 0 ? "MDC{" + options[0] + "}" : "MDC", "mdc");
48          key = options != null && options.length > 0 ? options[0] : null;
49      }
50  
51      /**
52       * Obtains an instance of PropertiesPatternConverter.
53       *
54       * @param options options, may be null or first element contains name of property to format.
55       * @return instance of PropertiesPatternConverter.
56       */
57      public static MDCPatternConverter newInstance(final String[] options) {
58          return new MDCPatternConverter(options);
59      }
60  
61      /**
62       * {@inheritDoc}
63       */
64      @Override
65      public void format(final LogEvent event, final StringBuilder toAppendTo) {
66          final Map<String, String> contextMap = event.getContextMap();
67          // if there is no additional options, we output every single
68          // Key/Value pair for the MDC in a similar format to Hashtable.toString()
69          if (key == null) {
70  
71  
72              if (contextMap == null || contextMap.size() == 0) {
73                  toAppendTo.append("{}");
74                  return;
75              }
76              final StringBuilder sb = new StringBuilder("{");
77              final Set<String> keys = new TreeSet<String>(contextMap.keySet());
78              for (final String key : keys) {
79                  if (sb.length() > 1) {
80                      sb.append(", ");
81                  }
82                  sb.append(key).append("=").append(contextMap.get(key));
83  
84              }
85              sb.append("}");
86              toAppendTo.append(sb);
87          } else if (contextMap != null) {
88              // otherwise they just want a single key output
89              final Object val = contextMap.get(key);
90  
91              if (val != null) {
92                  toAppendTo.append(val);
93              }
94          }
95      }
96  }