001package org.eclipse.aether.util.concurrency; 002 003/* 004 * Licensed to the Apache Software Foundation (ASF) under one 005 * or more contributor license agreements. See the NOTICE file 006 * distributed with this work for additional information 007 * regarding copyright ownership. The ASF licenses this file 008 * to you under the Apache License, Version 2.0 (the 009 * "License"); you may not use this file except in compliance 010 * with the License. You may obtain a copy of the License at 011 * 012 * http://www.apache.org/licenses/LICENSE-2.0 013 * 014 * Unless required by applicable law or agreed to in writing, 015 * software distributed under the License is distributed on an 016 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 017 * KIND, either express or implied. See the License for the 018 * specific language governing permissions and limitations 019 * under the License. 020 */ 021 022import static java.util.Objects.requireNonNull; 023 024import java.util.concurrent.atomic.AtomicInteger; 025import java.util.concurrent.atomic.AtomicReference; 026import java.util.concurrent.locks.LockSupport; 027 028/** 029 * A utility class to forward any uncaught {@link Error} or {@link RuntimeException} from a {@link Runnable} executed in 030 * a worker thread back to the parent thread. The simplified usage pattern looks like this: 031 * 032 * <pre> 033 * RunnableErrorForwarder errorForwarder = new RunnableErrorForwarder(); 034 * for ( Runnable task : tasks ) 035 * { 036 * executor.execute( errorForwarder.wrap( task ) ); 037 * } 038 * errorForwarder.await(); 039 * </pre> 040 */ 041public final class RunnableErrorForwarder 042{ 043 044 private final Thread thread = Thread.currentThread(); 045 046 private final AtomicInteger counter = new AtomicInteger(); 047 048 private final AtomicReference<Throwable> error = new AtomicReference<>(); 049 050 /** 051 * Creates a new error forwarder for worker threads spawned by the current thread. 052 */ 053 public RunnableErrorForwarder() 054 { 055 } 056 057 /** 058 * Wraps the specified runnable into an equivalent runnable that will allow forwarding of uncaught errors. 059 * 060 * @param runnable The runnable from which to forward errors, must not be {@code null}. 061 * @return The error-forwarding runnable to eventually execute, never {@code null}. 062 */ 063 public Runnable wrap( final Runnable runnable ) 064 { 065 requireNonNull( runnable, "runnable cannot be null" ); 066 067 counter.incrementAndGet(); 068 069 return new Runnable() 070 { 071 public void run() 072 { 073 try 074 { 075 runnable.run(); 076 } 077 catch ( RuntimeException | Error e ) 078 { 079 error.compareAndSet( null, e ); 080 throw e; 081 } 082 finally 083 { 084 counter.decrementAndGet(); 085 LockSupport.unpark( thread ); 086 } 087 } 088 }; 089 } 090 091 /** 092 * Causes the current thread to wait until all previously {@link #wrap(Runnable) wrapped} runnables have terminated 093 * and potentially re-throws an uncaught {@link RuntimeException} or {@link Error} from any of the runnables. In 094 * case multiple runnables encountered uncaught errors, one error is arbitrarily selected. <em>Note:</em> This 095 * method must be called from the same thread that created this error forwarder instance. 096 */ 097 public void await() 098 { 099 awaitTerminationOfAllRunnables(); 100 101 Throwable error = this.error.get(); 102 if ( error != null ) 103 { 104 if ( error instanceof RuntimeException ) 105 { 106 throw (RuntimeException) error; 107 } 108 else if ( error instanceof ThreadDeath ) 109 { 110 throw new IllegalStateException( error ); 111 } 112 else if ( error instanceof Error ) 113 { 114 throw (Error) error; 115 } 116 throw new IllegalStateException( error ); 117 } 118 } 119 120 private void awaitTerminationOfAllRunnables() 121 { 122 if ( !thread.equals( Thread.currentThread() ) ) 123 { 124 throw new IllegalStateException( "wrong caller thread, expected " + thread + " and not " 125 + Thread.currentThread() ); 126 } 127 128 boolean interrupted = false; 129 130 while ( counter.get() > 0 ) 131 { 132 LockSupport.park(); 133 134 if ( Thread.interrupted() ) 135 { 136 interrupted = true; 137 } 138 } 139 140 if ( interrupted ) 141 { 142 Thread.currentThread().interrupt(); 143 } 144 } 145 146}