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1   /**
2    * Logback: the reliable, generic, fast and flexible logging framework.
3    * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
4    *
5    * This program and the accompanying materials are dual-licensed under
6    * either the terms of the Eclipse Public License v1.0 as published by
7    * the Eclipse Foundation
8    *
9    *   or (per the licensee's choosing)
10   *
11   * under the terms of the GNU Lesser General Public License version 2.1
12   * as published by the Free Software Foundation.
13   */
14  package ch.qos.logback.classic.sift;
15  
16  import ch.qos.logback.classic.spi.ILoggingEvent;
17  import ch.qos.logback.core.sift.AbstractDiscriminator;
18  import ch.qos.logback.core.util.OptionHelper;
19  
20  import java.util.Map;
21  
22  /**
23   * MDCBasedDiscriminator essentially returns the value mapped to an MDC key. If
24   * the said value is null, then a default value is returned.
25   * <p/>
26   * <p>
27   * Both Key and the DefaultValue are user specified properties.
28   *
29   * @author Ceki G&uuml;lc&uuml;
30   */
31  public class MDCBasedDiscriminator extends AbstractDiscriminator<ILoggingEvent> {
32  
33      private String key;
34      private String defaultValue;
35  
36      /**
37       * Return the value associated with an MDC entry designated by the Key property.
38       * If that value is null, then return the value assigned to the DefaultValue
39       * property.
40       */
41      public String getDiscriminatingValue(ILoggingEvent event) {
42          // http://jira.qos.ch/browse/LBCLASSIC-213
43          Map<String, String> mdcMap = event.getMDCPropertyMap();
44          if (mdcMap == null) {
45              return defaultValue;
46          }
47          String mdcValue = mdcMap.get(key);
48          if (mdcValue == null) {
49              return defaultValue;
50          } else {
51              return mdcValue;
52          }
53      }
54  
55      @Override
56      public void start() {
57          int errors = 0;
58          if (OptionHelper.isNullOrEmpty(key)) {
59              errors++;
60              addError("The \"Key\" property must be set");
61          }
62          if (OptionHelper.isNullOrEmpty(defaultValue)) {
63              errors++;
64              addError("The \"DefaultValue\" property must be set");
65          }
66          if (errors == 0) {
67              started = true;
68          }
69      }
70  
71      public String getKey() {
72          return key;
73      }
74  
75      public void setKey(String key) {
76          this.key = key;
77      }
78  
79      /**
80       * @return
81       * @see #setDefaultValue(String)
82       */
83      public String getDefaultValue() {
84          return defaultValue;
85      }
86  
87      /**
88       * The default MDC value in case the MDC is not set for {@link #setKey(String)
89       * mdcKey}.
90       * <p/>
91       * <p>
92       * For example, if {@link #setKey(String) Key} is set to the value "someKey",
93       * and the MDC is not set for "someKey", then this appender will use the default
94       * value, which you can set with the help of this method.
95       *
96       * @param defaultValue
97       */
98      public void setDefaultValue(String defaultValue) {
99          this.defaultValue = defaultValue;
100     }
101 }