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
23   * does not disturb the functioning of the filter chain.
24   * 
25   * <p>
26   * It is expected that one of the two attributes will have its value changed to
27   * {@link FilterReply#ACCEPT} or {@link FilterReply#DENY}. That way, it is
28   * possible to decide if a given result must be returned after the evaluation
29   * either failed or succeeded.
30   * 
31   * 
32   * <p>
33   * For more information about filters, please refer to the online manual at
34   * http://logback.qos.ch/manual/filters.html
35   * 
36   * @author Ceki G&uuml;lc&uuml;
37   * @author S&eacute;bastien Pennec
38   */
39  public class EvaluatorFilter<E> extends AbstractMatcherFilter<E> {
40  
41      EventEvaluator<E> evaluator;
42  
43      @Override
44      public void start() {
45          if (evaluator != null) {
46              super.start();
47          } else {
48              addError("No evaluator set for filter " + this.getName());
49          }
50      }
51  
52      public EventEvaluator<E> getEvaluator() {
53          return evaluator;
54      }
55  
56      public void setEvaluator(EventEvaluator<E> evaluator) {
57          this.evaluator = evaluator;
58      }
59  
60      public FilterReply decide(E event) {
61          // let us not throw an exception
62          // see also bug #17.
63          if (!isStarted() || !evaluator.isStarted()) {
64              return FilterReply.NEUTRAL;
65          }
66          try {
67              if (evaluator.evaluate(event)) {
68                  return onMatch;
69              } else {
70                  return onMismatch;
71              }
72          } catch (EvaluationException e) {
73              addError("Evaluator " + evaluator.getName() + " threw an exception", e);
74              return FilterReply.NEUTRAL;
75          }
76      }
77  
78  }