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1   /*
2    * Copyright 2007 Tim Peierls
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * 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,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  package org.directwebremoting.guice;
17  
18  import com.google.inject.Provider;
19  
20  import java.util.concurrent.Callable;
21  import java.util.concurrent.ExecutionException;
22  import java.util.concurrent.FutureTask;
23  
24  /**
25   * A provider implementation that uses the FutureTask machinery.
26   * @author Tim Peierls [tim at peierls dot net]
27   */
28  class FutureTaskProvider<T> extends FutureTask<T> implements InstanceProvider<T>
29  {
30      FutureTaskProvider(final Provider<T> creator)
31      {
32          super(new Callable<T>()
33          {
34              public T call()
35              {
36                  return creator.get();
37              }
38          });
39      }
40      
41      @Override public T get()
42      {
43          try
44          {
45              return super.get();
46          }
47          catch (InterruptedException e)
48          {
49              Thread.currentThread().interrupt();
50              return null;
51          }
52          catch (ExecutionException e)
53          {
54              Throwable t = e.getCause();
55              if (t instanceof RuntimeException)
56              {
57                  throw (RuntimeException) t;
58              }
59              else if (t instanceof Error)
60              {
61                  throw (Error) t;
62              }
63              else
64              {
65                  throw new IllegalStateException("unexpected Exception: " + t, t);
66              }
67          }
68      }
69  }