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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 java.lang.reflect.InvocationTargetException;
23  import java.lang.reflect.Method;
24  import java.util.Arrays;
25  
26  import org.apache.commons.lang.builder.EqualsBuilder;
27  import org.apache.commons.lang.builder.HashCodeBuilder;
28  import org.apache.commons.lang.builder.ToStringBuilder;
29  import org.apache.mina.statemachine.State;
30  import org.apache.mina.statemachine.StateMachine;
31  import org.apache.mina.statemachine.StateMachineFactory;
32  import org.apache.mina.statemachine.annotation.Transition;
33  import org.apache.mina.statemachine.context.StateContext;
34  import org.apache.mina.statemachine.event.Event;
35  import org.slf4j.Logger;
36  import org.slf4j.LoggerFactory;
37  
38  /**
39   * {@link Transition} which invokes a {@link Method}. The {@link Method} will
40   * only be invoked if its argument types actually matches a subset of the 
41   * {@link Event}'s argument types. The argument types are matched in order so
42   * you must make sure the order of the method's arguments corresponds to the
43   * order of the event's arguments. 
44   *<p>
45   * If the first method argument type matches
46   * {@link Event} the current {@link Event} will be bound to that argument. In
47   * the same manner the second argument (or first if the method isn't interested 
48   * in the current {@link Event}) can have the {@link StateContext} type and will
49   * in that case be bound to the current {@link StateContext}.
50   * </p>
51   * <p>
52   * Normally you wouldn't create instances of this class directly but rather use the 
53   * {@link Transition} annotation to define the methods which should be used as
54   * transitions in your state machine and then let {@link StateMachineFactory} create a 
55   * {@link StateMachine} for you.
56   * </p>
57   *
58   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
59   */
60  public class MethodTransition extends AbstractTransition {
61      private static final Logger LOGGER = LoggerFactory.getLogger(MethodTransition.class);
62  
63      private static final Object[] EMPTY_ARGUMENTS = new Object[0];
64  
65      private final Method method;
66  
67      private final Object target;
68  
69      /**
70       * Creates a new instance with the specified {@link State} as next state 
71       * and for the specified {@link Event} id.
72       * 
73       * @param eventId the {@link Event} id.
74       * @param nextState the next {@link State}.
75       * @param method the target method.
76       * @param target the target object.
77       */
78      public MethodTransition(Object eventId, State nextState, Method method, Object target) {
79          super(eventId, nextState);
80          this.method = method;
81          this.target = target;
82      }
83  
84      /**
85       * Creates a new instance which will loopback to the same {@link State} 
86       * for the specified {@link Event} id.
87       * 
88       * @param eventId the {@link Event} id.
89       * @param method the target method.
90       * @param target the target object.
91       */
92      public MethodTransition(Object eventId, Method method, Object target) {
93          this(eventId, null, method, target);
94      }
95  
96      /**
97       * Creates a new instance with the specified {@link State} as next state 
98       * and for the specified {@link Event} id. The target {@link Method} will
99       * be the method in the specified target object with the same name as the
100      * specified {@link Event} id.
101      * 
102      * @param eventId the {@link Event} id.
103      * @param nextState the next {@link State}.
104      * @param target the target object.
105      * @throws NoSuchMethodException if no method could be found with a name 
106      *         equal to the {@link Event} id.
107      * @throws AmbiguousMethodException if more than one method was found with 
108      *         a name equal to the {@link Event} id.
109      */
110     public MethodTransition(Object eventId, State nextState, Object target) {
111         this(eventId, nextState, eventId.toString(), target);
112     }
113 
114     /**
115      * Creates a new instance which will loopback to the same {@link State} 
116      * for the specified {@link Event} id. The target {@link Method} will
117      * be the method in the specified target object with the same name as the
118      * specified {@link Event} id.
119      * 
120      * @param eventId the {@link Event} id.
121      * @param target the target object.
122      * @throws NoSuchMethodException if no method could be found with a name 
123      *         equal to the {@link Event} id.
124      * @throws AmbiguousMethodException if more than one method was found with 
125      *         a name equal to the {@link Event} id.
126      */
127     public MethodTransition(Object eventId, Object target) {
128         this(eventId, eventId.toString(), target);
129     }
130 
131     /**
132      * Creates a new instance which will loopback to the same {@link State} 
133      * for the specified {@link Event} id.
134      * 
135      * @param eventId the {@link Event} id.
136      * @param methodName the name of the target {@link Method}.
137      * @param target the target object.
138      * @throws NoSuchMethodException if the method could not be found.
139      * @throws AmbiguousMethodException if there are more than one method with 
140      *         the specified name.
141      */
142     public MethodTransition(Object eventId, String methodName, Object target) {
143         this(eventId, null, methodName, target);
144     }
145 
146     /**
147      * Creates a new instance with the specified {@link State} as next state 
148      * and for the specified {@link Event} id.
149      * 
150      * @param eventId the {@link Event} id.
151      * @param nextState the next {@link State}.
152      * @param methodName the name of the target {@link Method}.
153      * @param target the target object.
154      * @throws NoSuchMethodException if the method could not be found.
155      * @throws AmbiguousMethodException if there are more than one method with 
156      *         the specified name.
157      */
158     public MethodTransition(Object eventId, State nextState, String methodName, Object target) {
159         super(eventId, nextState);
160 
161         this.target = target;
162 
163         Method[] candidates = target.getClass().getMethods();
164         Method result = null;
165         for (int i = 0; i < candidates.length; i++) {
166             if (candidates[i].getName().equals(methodName)) {
167                 if (result != null) {
168                     throw new AmbiguousMethodException(methodName);
169                 }
170                 result = candidates[i];
171             }
172         }
173 
174         if (result == null) {
175             throw new NoSuchMethodException(methodName);
176         }
177 
178         this.method = result;
179     }
180 
181     /**
182      * Returns the target {@link Method}.
183      * 
184      * @return the method.
185      */
186     public Method getMethod() {
187         return method;
188     }
189 
190     /**
191      * Returns the target object.
192      * 
193      * @return the target object.
194      */
195     public Object getTarget() {
196         return target;
197     }
198 
199     public boolean doExecute(Event event) {
200         Class<?>[] types = method.getParameterTypes();
201 
202         if (types.length == 0) {
203             invokeMethod(EMPTY_ARGUMENTS);
204             return true;
205         }
206 
207         if (types.length > 2 + event.getArguments().length) {
208             return false;
209         }
210 
211         Object[] args = new Object[types.length];
212 
213         int i = 0;
214         if (match(types[i], event, Event.class)) {
215             args[i++] = event;
216         }
217         if (i < args.length && match(types[i], event.getContext(), StateContext.class)) {
218             args[i++] = event.getContext();
219         }
220         Object[] eventArgs = event.getArguments();
221         for (int j = 0; i < args.length && j < eventArgs.length; j++) {
222             if (match(types[i], eventArgs[j], Object.class)) {
223                 args[i++] = eventArgs[j];
224             }
225         }
226 
227         if (args.length > i) {
228             return false;
229         }
230 
231         invokeMethod(args);
232 
233         return true;
234     }
235 
236     @SuppressWarnings("unchecked")
237     private boolean match(Class<?> paramType, Object arg, Class argType) {
238         if (paramType.isPrimitive()) {
239             if (paramType.equals(Boolean.TYPE)) {
240                 return arg instanceof Boolean;
241             }
242             if (paramType.equals(Integer.TYPE)) {
243                 return arg instanceof Integer;
244             }
245             if (paramType.equals(Long.TYPE)) {
246                 return arg instanceof Long;
247             }
248             if (paramType.equals(Short.TYPE)) {
249                 return arg instanceof Short;
250             }
251             if (paramType.equals(Byte.TYPE)) {
252                 return arg instanceof Byte;
253             }
254             if (paramType.equals(Double.TYPE)) {
255                 return arg instanceof Double;
256             }
257             if (paramType.equals(Float.TYPE)) {
258                 return arg instanceof Float;
259             }
260             if (paramType.equals(Character.TYPE)) {
261                 return arg instanceof Character;
262             }
263         }
264         return argType.isAssignableFrom(paramType) && paramType.isAssignableFrom(arg.getClass());
265     }
266 
267     private void invokeMethod(Object[] arguments) {
268         try {
269             if (LOGGER.isDebugEnabled()) {
270                 LOGGER.debug("Executing method " + method + " with arguments " + Arrays.asList(arguments));
271             }
272             method.invoke(target, arguments);
273         } catch (InvocationTargetException ite) {
274             if (ite.getCause() instanceof RuntimeException) {
275                 throw (RuntimeException) ite.getCause();
276             }
277             throw new MethodInvocationException(method, ite);
278         } catch (IllegalAccessException iae) {
279             throw new MethodInvocationException(method, iae);
280         }
281     }
282 
283     public boolean equals(Object o) {
284         if (!(o instanceof MethodTransition)) {
285             return false;
286         }
287         if (o == this) {
288             return true;
289         }
290         MethodTransition that = (MethodTransition) o;
291         return new EqualsBuilder().appendSuper(super.equals(that)).append(method, that.method)
292                 .append(target, that.target).isEquals();
293     }
294 
295     public int hashCode() {
296         return new HashCodeBuilder(13, 33).appendSuper(super.hashCode()).append(method).append(target).toHashCode();
297     }
298 
299     public String toString() {
300         return new ToStringBuilder(this).appendSuper(super.toString()).append("method", method)
301                 .append("target", target).toString();
302     }
303 }