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1   /**
2    * Logback: the reliable, generic, fast and flexible logging framework.
3    * Copyright (C) 1999-2009, 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 Filter.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 Filter.ACCEPT} or {@link Filter.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  }