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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.context;
21  
22  /**
23   * Abstract {@link StateContextLookup} implementation. The {@link #lookup(Object[])}
24   * method will loop through the event arguments and call the {@link #supports(Class)}
25   * method for each of them. The first argument that this method returns 
26   * <code>true</code> for will be passed to the abstract {@link #lookup(Object)}
27   * method which should try to extract a {@link StateContext} from the argument.
28   * If none is found a new {@link StateContext} will be created and stored in the
29   * event argument using the {@link #store(Object, StateContext)} method.
30   *
31   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
32   */
33  public abstract class AbstractStateContextLookup implements StateContextLookup {
34      private final StateContextFactory contextFactory;
35  
36      /**
37       * Creates a new instance which uses the specified {@link StateContextFactory}
38       * to create {@link StateContext} objects.
39       * 
40       * @param contextFactory the factory.
41       */
42      public AbstractStateContextLookup(StateContextFactory contextFactory) {
43          if (contextFactory == null) {
44              throw new IllegalArgumentException("contextFactory");
45          }
46          this.contextFactory = contextFactory;
47      }
48  
49      public StateContext lookup(Object[] eventArgs) {
50          for (int i = 0; i < eventArgs.length; i++) {
51              if (supports(eventArgs[i].getClass())) {
52                  StateContext sc = lookup(eventArgs[i]);
53                  if (sc == null) {
54                      sc = contextFactory.create();
55                      store(eventArgs[i], sc);
56                  }
57                  return sc;
58              }
59          }
60          return null;
61      }
62  
63      /**
64       * Extracts a {@link StateContext} from the specified event argument which
65       * is an instance of a class {@link #supports(Class)} returns 
66       * <code>true</code> for.
67       * 
68       * @param eventArg the event argument.
69       * @return the {@link StateContext}.
70       */
71      protected abstract StateContext lookup(Object eventArg);
72  
73      /**
74       * Stores a new {@link StateContext} in the specified event argument which
75       * is an instance of a class {@link #supports(Class)} returns 
76       * <code>true</code> for.
77       * 
78       * @param eventArg the event argument.
79       * @param context the {@link StateContext} to be stored.
80       */
81      protected abstract void store(Object eventArg, StateContext context);
82  
83      /**
84       * Must return <code>true</code> for any {@link Class} that this
85       * {@link StateContextLookup} can use to store and lookup 
86       * {@link StateContext} objects.
87       * 
88       * @param c the class.
89       * @return <code>true</code> or <code>false</code>.
90       */
91      protected abstract boolean supports(Class<?> c);
92  }