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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.core.sift;
15  
16  import ch.qos.logback.core.spi.LifeCycle;
17  
18  /**
19   * Implement this interface in order to compute a discriminating value for a
20   * given event of type <E>.
21   * 
22   * <p>The returned value can depend on any data available at the time of the
23   * call, including data contained within the currently running thread.
24   * 
25   * @author Ceki G&uuml;lc&uuml;
26   * 
27   * @param <E>
28   */
29  public interface Discriminator<E> extends LifeCycle {
30  
31      /**
32       * Given event 'e' return a discriminating value.
33       * 
34       * @param e
35       * @return
36       */
37      String getDiscriminatingValue(E e);
38  
39      /**
40       * The key or variable name under which the discriminating value should be
41       * exported into the host environment. 
42       *
43       * @return
44       */
45      String getKey();
46  }