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 * The interface implemented by classes which need to react on transitions
28 * between states.
29 *
30 * @author The Apache MINA Project (dev@mina.apache.org)
31 * @version $Rev: 586695 $, $Date: 2007-10-20 12:01:17 +0200 (sam, 20 oct 2007) $
32 */
33 public interface Transition {
34 /**
35 * Executes this {@link Transition}. It is the responsibility of this
36 * {@link Transition} to determine whether it actually applies for the
37 * specified {@link Event}. If this {@link Transition} doesn't apply
38 * nothing should be executed and <code>false</code> must be returned.
39 *
40 * @param event the current {@link Event}.
41 * @return <code>true</code> if the {@link Transition} was executed,
42 * <code>false</code> otherwise.
43 */
44 boolean execute(Event event);
45
46 /**
47 * Returns the {@link State} which the {@link StateMachine} should move to
48 * if this {@link Transition} is taken and {@link #execute(Event)} returns
49 * <code>true</code>.
50 *
51 * @return the next {@link State} or <code>null</code> if this
52 * {@link Transition} is a loopback {@link Transition}.
53 */
54 State getNextState();
55 }