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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing,
13   * software distributed under the License is distributed on an
14   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15   * KIND, either express or implied.  See the License for the
16   * specific language governing permissions and limitations
17   * under the License.
18   */
19  package org.apache.shiro.event.support;
20  
21  import org.apache.shiro.event.Subscribe;
22  import org.apache.shiro.util.ClassUtils;
23  
24  import java.lang.annotation.Annotation;
25  import java.lang.reflect.Method;
26  import java.util.ArrayList;
27  import java.util.Collections;
28  import java.util.List;
29  
30  /**
31   * Inspects an object for annotated methods of interest and creates an {@link EventListener} instance for each method
32   * discovered.  An event bus will call the resulting listeners as relevant events arrive.
33   * <p/>
34   * The default {@link #setAnnotationClass(Class) annotationClass} is {@link Subscribe}, indicating each
35   * {@link Subscribe}-annotated method will be represented as an EventListener.
36   *
37   * @see SingleArgumentMethodEventListener
38   * @since 1.3
39   */
40  public class AnnotationEventListenerResolver implements EventListenerResolver {
41  
42      private Class<? extends Annotation> annotationClass;
43  
44      public AnnotationEventListenerResolver() {
45          this.annotationClass = Subscribe.class;
46      }
47  
48      /**
49       * Returns a new collection of {@link EventListener} instances, each instance corresponding to an annotated
50       * method discovered on the specified {@code instance} argument.
51       *
52       * @param instance the instance to inspect for annotated event handler methods.
53       * @return a new collection of {@link EventListener} instances, each instance corresponding to an annotated
54       *         method discovered on the specified {@code instance} argument.
55       */
56      public List<EventListener> getEventListeners(Object instance) {
57          if (instance == null) {
58              return Collections.emptyList();
59          }
60  
61          List<Method> methods = ClassUtils.getAnnotatedMethods(instance.getClass(), getAnnotationClass());
62          if (methods == null || methods.isEmpty()) {
63              return Collections.emptyList();
64          }
65  
66          List<EventListener> listeners = new ArrayList<EventListener>(methods.size());
67  
68          for (Method m : methods) {
69              listeners.add(new SingleArgumentMethodEventListener(instance, m));
70          }
71  
72          return listeners;
73      }
74  
75      /**
76       * Returns the type of annotation that indicates a method that should be represented as an {@link EventListener},
77       * defaults to {@link Subscribe}.
78       *
79       * @return the type of annotation that indicates a method that should be represented as an {@link EventListener},
80       *         defaults to {@link Subscribe}.
81       */
82      public Class<? extends Annotation> getAnnotationClass() {
83          return annotationClass;
84      }
85  
86      /**
87       * Sets the type of annotation that indicates a method that should be represented as an {@link EventListener}.
88       * The default value is {@link Subscribe}.
89       *
90       * @param annotationClass the type of annotation that indicates a method that should be represented as an
91       *                        {@link EventListener}.  The default value is {@link Subscribe}.
92       */
93      public void setAnnotationClass(Class<? extends Annotation> annotationClass) {
94          this.annotationClass = annotationClass;
95      }
96  }