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1   /*
2    * Copyright 2012 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. You may obtain a copy of the License at:
7    *
8    *   http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  package org.jboss.netty.handler.execution;
17  
18  
19  import java.util.concurrent.Executor;
20  import java.util.concurrent.ExecutorService;
21  
22  import org.jboss.netty.util.ExternalResourceReleasable;
23  
24  /**
25   * A special {@link Executor} which allows to chain a series of
26   * {@link Executor}s and {@link ChannelEventRunnableFilter}.
27   */
28  public class ChainedExecutor implements Executor, ExternalResourceReleasable {
29  
30      private final Executor cur;
31      private final Executor next;
32      private final ChannelEventRunnableFilter filter;
33  
34      /**
35       * Create a new {@link ChainedExecutor} which will used the given
36       * {@link ChannelEventRunnableFilter} to see if the {@link #cur} {@link Executor} should get
37       * used.  Otherwise it will pass the work to the {@link #next} {@link Executor}
38       *
39       * @param filter  the {@link ChannelEventRunnableFilter} which will be used to check if the
40       *                {@link ChannelEventRunnable} should be passed to the cur or next {@link Executor}
41       * @param cur     the {@link Executor} to use if the {@link ChannelEventRunnableFilter} match
42       * @param next    the {@link Executor} to use if the {@link ChannelEventRunnableFilter} does not match
43       */
44      public ChainedExecutor(ChannelEventRunnableFilter filter, Executor cur, Executor next) {
45          if (filter == null) {
46              throw new NullPointerException("filter");
47          }
48          if (cur == null) {
49              throw new NullPointerException("cur");
50          }
51          if (next == null) {
52              throw new NullPointerException("next");
53          }
54  
55          this.filter = filter;
56          this.cur = cur;
57          this.next = next;
58      }
59  
60      /**
61       * Execute the passed {@link ChannelEventRunnable} with the current {@link Executor} if the
62       * {@link ChannelEventRunnableFilter} match.  Otherwise pass it to the next {@link Executor} in
63       * the chain.
64       */
65      public void execute(Runnable command) {
66          assert command instanceof ChannelEventRunnable;
67          if (filter.filter((ChannelEventRunnable) command)) {
68              cur.execute(command);
69          } else {
70              next.execute(command);
71          }
72      }
73  
74      public void releaseExternalResources() {
75          if (cur instanceof ExecutorService) {
76              ((ExecutorService) cur).shutdown();
77          }
78          if (next instanceof ExecutorService) {
79              ((ExecutorService) next).shutdown();
80          }
81          releaseExternal(cur);
82          releaseExternal(next);
83      }
84  
85      private static void releaseExternal(Executor executor) {
86          if (executor instanceof ExternalResourceReleasable) {
87              ((ExternalResourceReleasable) executor).releaseExternalResources();
88          }
89      }
90  }