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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   */
20  package org.apache.mina.statemachine.transition;
21  
22  import org.apache.commons.lang.builder.EqualsBuilder;
23  import org.apache.commons.lang.builder.HashCodeBuilder;
24  import org.apache.commons.lang.builder.ToStringBuilder;
25  import org.apache.mina.statemachine.State;
26  import org.apache.mina.statemachine.StateMachine;
27  import org.apache.mina.statemachine.event.Event;
28  
29  /**
30   * Abstract {@link Transition} implementation. Takes care of matching the
31   * current {@link Event}'s id against the id of the {@link Event} this 
32   * {@link Transition} handles. To handle any {@link Event} the id should be set
33   * to {@link Event#WILDCARD_EVENT_ID}.
34   *
35   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
36   */
37  public abstract class AbstractTransition implements Transition {
38      private final Object eventId;
39  
40      private final State nextState;
41  
42      /**
43       * Creates a new instance which will loopback to the same {@link State} 
44       * for the specified {@link Event} id.
45       * 
46       * @param eventId the {@link Event} id.
47       */
48      public AbstractTransition(Object eventId) {
49          this(eventId, null);
50      }
51  
52      /**
53       * Creates a new instance with the specified {@link State} as next state 
54       * and for the specified {@link Event} id.
55       * 
56       * @param eventId the {@link Event} id.
57       * @param nextState the next {@link State}.
58       */
59      public AbstractTransition(Object eventId, State nextState) {
60          this.eventId = eventId;
61          this.nextState = nextState;
62      }
63  
64      public State getNextState() {
65          return nextState;
66      }
67  
68      public boolean execute(Event event) {
69          if (!eventId.equals(Event.WILDCARD_EVENT_ID) && !eventId.equals(event.getId())) {
70              return false;
71          }
72  
73          return doExecute(event);
74      }
75  
76      /**
77       * Executes this {@link Transition}. This method doesn't have to check
78       * if the {@link Event}'s id matches because {@link #execute(Event)} has
79       * already made sure that that is the case.
80       * 
81       * @param event the current {@link Event}.
82       * @return <code>true</code> if the {@link Transition} has been executed 
83       *         successfully and the {@link StateMachine} should move to the 
84       *         next {@link State}. <code>false</code> otherwise.
85       */
86      protected abstract boolean doExecute(Event event);
87  
88      public boolean equals(Object o) {
89          if (!(o instanceof AbstractTransition)) {
90              return false;
91          }
92          if (o == this) {
93              return true;
94          }
95          AbstractTransition that = (AbstractTransition) o;
96          return new EqualsBuilder().append(eventId, that.eventId).append(nextState, that.nextState).isEquals();
97      }
98  
99      public int hashCode() {
100         return new HashCodeBuilder(11, 31).append(eventId).append(nextState).toHashCode();
101     }
102 
103     public String toString() {
104         return new ToStringBuilder(this).append("eventId", eventId).append("nextState", nextState).toString();
105     }
106 }