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>
23   * The returned value can depend on any data available at the time of the call,
24   * including data contained within the currently running thread.
25   * 
26   * @author Ceki G&uuml;lc&uuml;
27   * 
28   * @param <E>
29   */
30  public interface Discriminator<E> extends LifeCycle {
31  
32      /**
33       * Given event 'e' return a discriminating value.
34       * 
35       * @param e
36       * @return
37       */
38      String getDiscriminatingValue(E e);
39  
40      /**
41       * The key or variable name under which the discriminating value should be
42       * exported into the host environment.
43       *
44       * @return
45       */
46      String getKey();
47  }