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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.filter;
15  
16  import ch.qos.logback.core.boolex.EvaluationException;
17  import ch.qos.logback.core.boolex.EventEvaluator;
18  import ch.qos.logback.core.spi.FilterReply;
19  
20  /**
21   * The value of the {@link #onMatch} and {@link #onMismatch} attributes is set
22   * to {@link FilterReply#NEUTRAL}, so that a badly configured evaluator filter does
23   * not disturb the functioning of the filter chain. 
24   * 
25   * <p>It is expected that one of the two attributes will have its value changed
26   * to {@link FilterReply#ACCEPT} or {@link FilterReply#DENY}. That way, it is possible to
27   * decide if a given result must be returned after the evaluation either failed
28   * or succeeded.
29   * 
30   * 
31   * <p> For more information about filters, please refer to the online manual at
32   * http://logback.qos.ch/manual/filters.html
33   * 
34   * @author Ceki G&uuml;lc&uuml;
35   * @author S&eacute;bastien Pennec
36   */
37  public class EvaluatorFilter<E> extends AbstractMatcherFilter<E> {
38  
39      EventEvaluator<E> evaluator;
40  
41      @Override
42      public void start() {
43          if (evaluator != null) {
44              super.start();
45          } else {
46              addError("No evaluator set for filter " + this.getName());
47          }
48      }
49  
50      public EventEvaluator<E> getEvaluator() {
51          return evaluator;
52      }
53  
54      public void setEvaluator(EventEvaluator<E> evaluator) {
55          this.evaluator = evaluator;
56      }
57  
58      public FilterReply decide(E event) {
59          // let us not throw an exception
60          // see also bug #17.
61          if (!isStarted() || !evaluator.isStarted()) {
62              return FilterReply.NEUTRAL;
63          }
64          try {
65              if (evaluator.evaluate(event)) {
66                  return onMatch;
67              } else {
68                  return onMismatch;
69              }
70          } catch (EvaluationException e) {
71              addError("Evaluator " + evaluator.getName() + " threw an exception", e);
72              return FilterReply.NEUTRAL;
73          }
74      }
75  
76  }