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1   /*
2    * $Id: FutureMessageResult.java 10489 2008-01-23 17:53:38Z dfeist $
3    * --------------------------------------------------------------------------------------
4    * Copyright (c) MuleSource, Inc.  All rights reserved.  http://www.mulesource.com
5    *
6    * The software in this package is published under the terms of the CPAL v1.0
7    * license, a copy of which has been included with this distribution in the
8    * LICENSE.txt file.
9    */
10  
11  package org.mule.api;
12  
13  import org.mule.DefaultMuleMessage;
14  import org.mule.api.transformer.TransformerException;
15  import org.mule.util.concurrent.DaemonThreadFactory;
16  
17  import java.util.List;
18  
19  import edu.emory.mathcs.backport.java.util.concurrent.Callable;
20  import edu.emory.mathcs.backport.java.util.concurrent.ExecutionException;
21  import edu.emory.mathcs.backport.java.util.concurrent.Executor;
22  import edu.emory.mathcs.backport.java.util.concurrent.Executors;
23  import edu.emory.mathcs.backport.java.util.concurrent.FutureTask;
24  import edu.emory.mathcs.backport.java.util.concurrent.TimeUnit;
25  import edu.emory.mathcs.backport.java.util.concurrent.TimeoutException;
26  
27  /**
28   * <code>FutureMessageResult</code> is an MuleMessage result of a remote invocation
29   * on a Mule Server. This object makes the result available to the client code once
30   * the request has been processed. This execution happens asynchronously.
31   */
32  // @ThreadSafe
33  public class FutureMessageResult extends FutureTask
34  {
35      /**
36       * This is a simple default Executor for FutureMessageResults. Instead of
37       * spawning a Thread for each invocation it uses a single daemon Thread with an
38       * unbounded queue, so "truly" concurrent operation of multiple Futures or
39       * otherwise customized execution behaviour requires calling the
40       * {@link #setExecutor(Executor)} method and passing in a custom {@link Executor}.
41       * This is strongly recommended in order to provide better control over
42       * concurrency, resource consumption and possible overruns.
43       * <p>
44       * Reasons for these defaults:
45       * <ul>
46       * <li> a daemon thread does not block the VM on shutdown; lifecycle control
47       * should be done elsewhere (e.g. the provider of the custom ExecutorService),
48       * otherwise this class would become too overloaded
49       * <li> a single thread provides for conservative & predictable yet async
50       * behaviour from a client's point of view
51       * <li> the unbounded queue is not optimal but probably harmless since e.g. a
52       * MuleClient would have to create a LOT of Futures for an OOM. Cancelled/timed
53       * out invocations are GC'ed so the problem is rather unlikely to occur.
54       * </ul>
55       */
56      private static final Executor DefaultExecutor = Executors.newSingleThreadExecutor(
57          new DaemonThreadFactory("MuleDefaultFutureMessageExecutor"));
58  
59      // @GuardedBy(this)
60      private Executor executor;
61  
62      // @GuardedBy(this)
63      private List transformers;
64  
65      public FutureMessageResult(Callable callable)
66      {
67          super(callable);
68          this.executor = DefaultExecutor;
69      }
70  
71      /**
72       * Set an ExecutorService to run this invocation.
73       * 
74       * @param e the executor to be used.
75       * @throws IllegalArgumentException when the executor is null or shutdown.
76       */
77      public void setExecutor(Executor e)
78      {
79          if (e == null)
80          {
81              throw new IllegalArgumentException("Executor must not be null.");
82          }
83  
84          synchronized (this)
85          {
86              this.executor = e;
87          }
88      }
89  
90      /**
91       * Set a post-invocation transformer.
92       * 
93       * @param t UMOTransformers to be applied to the result of this invocation. May be
94       *            null.
95       */
96      public void setTransformers(List t)
97      {
98          synchronized (this)
99          {
100             this.transformers = t;
101         }
102     }
103 
104     public MuleMessage getMessage() throws InterruptedException, ExecutionException, TransformerException
105     {
106         return this.getMessage(this.get());
107     }
108 
109     public MuleMessage getMessage(long timeout)
110         throws InterruptedException, ExecutionException, TimeoutException, TransformerException
111     {
112         return this.getMessage(this.get(timeout, TimeUnit.MILLISECONDS));
113     }
114 
115     private MuleMessage getMessage(Object obj) throws TransformerException
116     {
117         MuleMessage result = null;
118         if (obj != null)
119         {
120             if (obj instanceof MuleMessage)
121             {
122                 result = (MuleMessage)obj;
123             }
124             else
125             {
126                 result = new DefaultMuleMessage(obj);
127             }
128 
129             synchronized (this)
130             {
131                 if (transformers != null)
132                 {
133                     result.applyTransformers(transformers);
134                 }
135             }
136 
137         }
138         return result;
139     }
140 
141     /**
142      * Start asynchronous execution of this task
143      */
144     public void execute()
145     {
146         synchronized (this)
147         {
148             executor.execute(this);
149         }
150     }
151 
152 }