001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    
018    package org.apache.commons.proxy.interceptor;
019    
020    import EDU.oswego.cs.dl.util.concurrent.Executor;
021    import org.apache.commons.proxy.Invocation;
022    import org.apache.commons.proxy.Interceptor;
023    
024    /**
025     * A method interceptor that uses an {@link Executor} to execute the method invocation.
026     * <p/>
027     * <b>Note</b>: Only <em>void</em> methods can be intercepted using this class!  Any attempts to intercept non-void
028     * methods will result in an {@link IllegalArgumentException}.  If the proxy interfaces include non-void methods, try
029     * using a {@link FilteredInterceptor} along with a
030     * {@link org.apache.commons.proxy.interceptor.filter.ReturnTypeFilter} to wrap an instance of this class.
031     *
032     * <p>
033     * <b>Dependencies</b>:
034     * <ul>
035     *   <li>Concurrent API version 1.3.4 or greater</li>
036     * </ul>
037     * </p>
038     * @author James Carman
039     * @since 1.0
040     */
041    public class ExecutorInterceptor implements Interceptor
042    {
043        private final Executor executor;
044    
045        public ExecutorInterceptor( Executor executor )
046        {
047            this.executor = executor;
048        }
049    
050        public Object intercept( final Invocation invocation ) throws Throwable
051        {
052            if( Void.TYPE.equals( invocation.getMethod().getReturnType() ) )
053            {
054                // Special case for finalize() method (should not be run in a different thread)...
055                if( !( invocation.getMethod().getName().equals( "finalize" ) &&
056                       invocation.getMethod().getParameterTypes().length == 0 ) )
057                {
058                    executor.execute( new Runnable()
059                    {
060                        public void run()
061                        {
062                            try
063                            {
064                                invocation.proceed();
065                            }
066                            catch( Throwable t )
067                            {
068                                // What to do here?  I can't convey the failure back to the caller.
069                            }
070                        }
071                    } );
072                    return null;
073                }
074                else
075                {
076                    return invocation.proceed();
077                }
078            }
079            else
080            {
081                throw new IllegalArgumentException( "Only void methods can be executed in a different thread." );
082            }
083        }
084    }