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 */
20 package org.apache.mina.statemachine.transition;
21
22 import org.apache.mina.statemachine.State;
23 import org.apache.mina.statemachine.StateMachine;
24 import org.apache.mina.statemachine.event.Event;
25
26 /**
27 * Abstract {@link Transition} implementation. Takes care of matching the
28 * current {@link Event}'s id against the id of the {@link Event} this
29 * {@link Transition} handles. To handle any {@link Event} the id should be set
30 * to {@link Event#WILDCARD_EVENT_ID}.
31 *
32 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
33 */
34 public abstract class AbstractTransition implements Transition {
35 /** The accepted event ID */
36 private final Object eventId;
37
38 /** The next state, if any */
39 private final State nextState;
40
41 /**
42 * Creates a new instance which will loopback to the same {@link State}
43 * for the specified {@link Event} id.
44 *
45 * @param eventId the {@link Event} id.
46 */
47 public AbstractTransition(Object eventId) {
48 this(eventId, null);
49 }
50
51 /**
52 * Creates a new instance with the specified {@link State} as next state
53 * and for the specified {@link Event} id.
54 *
55 * @param eventId the {@link Event} id.
56 * @param nextState the next {@link State}.
57 */
58 public AbstractTransition(Object eventId, State nextState) {
59 this.eventId = eventId;
60 this.nextState = nextState;
61 }
62
63 /**
64 * Creates a new instance with the specified {@link State} as next state
65 * and for the wild card {@link Event} id.
66 *
67 * @param nextState the next {@link State}.
68 */
69 public AbstractTransition(State nextState) {
70 this.eventId = Event.WILDCARD_EVENT_ID;
71 this.nextState = nextState;
72 }
73
74 /**
75 * Creates a new instance with a reflexive {@link State} as next state
76 * and for the wild card {@link Event} id.
77 */
78 public AbstractTransition() {
79 this.eventId = Event.WILDCARD_EVENT_ID;
80 this.nextState = null;
81 }
82
83 /**
84 * {@inheritDoc}
85 */
86 @Override
87 public State getNextState() {
88 return nextState;
89 }
90
91 /**
92 * {@inheritDoc}
93 */
94 @Override
95 public boolean execute(Event event) {
96 if (!eventId.equals(Event.WILDCARD_EVENT_ID) && !eventId.equals(event.getId())) {
97 return false;
98 }
99
100 return doExecute(event);
101 }
102
103 /**
104 * Executes this {@link Transition}. This method doesn't have to check
105 * if the {@link Event}'s id matches because {@link #execute(Event)} has
106 * already made sure that that is the case.
107 *
108 * @param event the current {@link Event}.
109 * @return <tt>true</tt> if the {@link Transition} has been executed
110 * successfully and the {@link StateMachine} should move to the
111 * next {@link State}. <tt>false</tt> otherwise.
112 */
113 protected abstract boolean doExecute(Event event);
114
115 @Override
116 public boolean equals(Object o) {
117 if (o == this) {
118 return true;
119 }
120
121 if (!(o instanceof AbstractTransition)) {
122 return false;
123 }
124
125 AbstractTransition./../org/apache/mina/statemachine/transition/AbstractTransition.html#AbstractTransition">AbstractTransition that = (AbstractTransition) o;
126
127 if (eventId != null) {
128 if (!eventId.equals( that.eventId )) {
129 return false;
130 }
131 } else {
132 if (that.eventId != null) {
133 return false;
134 }
135 }
136
137
138 if (nextState != null) {
139 return nextState.equals( that.nextState );
140 } else {
141 return that.nextState == null;
142 }
143 }
144
145 @Override
146 public int hashCode() {
147 int h = 17;
148
149 if ( eventId != null) {
150 h = h*37 + eventId.hashCode();
151 }
152
153 if (nextState != null) {
154 h = h*17 + nextState.hashCode();
155 }
156
157 return h;
158 }
159
160 @Override
161 public String toString() {
162 StringBuilder sb = new StringBuilder();
163
164 sb.append("eventId=").append(eventId);
165 sb.append(",nextState=").append(nextState);
166
167 return sb.toString();
168 }
169 }