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 java.util.Comparator;
22
23 /**
24 * Compares two event listeners to determine the order in which they should be invoked when an event is dispatched.
25 * The lower the order, the sooner it will be invoked (the higher its precedence). The higher the order, the later
26 * it will be invoked (the lower its precedence).
27 * <p/>
28 * TypedEventListeners have a higher precedence (i.e. a lower order) than standard EventListener instances. Standard
29 * EventListener instances have the same order priority.
30 * <p/>
31 * When both objects being compared are TypedEventListeners, they are ordered according to the rules of the
32 * {@link EventClassComparator}, using the TypedEventListeners'
33 * {@link TypedEventListener#getEventType() eventType}.
34 *
35 * @since 1.3
36 */
37 public class EventListenerComparator implements Comparator<EventListener> {
38
39 //event class comparator is stateless, so we can retain an instance:
40 private static final EventClassComparatorl#EventClassComparator">EventClassComparator EVENT_CLASS_COMPARATOR = new EventClassComparator();
41
42 public int compare(EventListener../../../../../org/apache/shiro/event/support/EventListener.html#EventListener">EventListener a, EventListener b) {
43 if (a == null) {
44 if (b == null) {
45 return 0;
46 } else {
47 return -1;
48 }
49 } else if (b == null) {
50 return 1;
51 } else if (a == b || a.equals(b)) {
52 return 0;
53 } else {
54 if (a instanceof TypedEventListener) {
55 TypedEventListener/../../org/apache/shiro/event/support/TypedEventListener.html#TypedEventListener">TypedEventListener ta = (TypedEventListener)a;
56 if (b instanceof TypedEventListener) {
57 TypedEventListener/../../org/apache/shiro/event/support/TypedEventListener.html#TypedEventListener">TypedEventListener tb = (TypedEventListener)b;
58 return EVENT_CLASS_COMPARATOR.compare(ta.getEventType(), tb.getEventType());
59 } else {
60 return -1; //TypedEventListeners are 'less than' (higher priority) than non typed
61 }
62 } else {
63 if (b instanceof TypedEventListener) {
64 return 1;
65 } else {
66 return 0;
67 }
68 }
69 }
70 }
71 }