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 () -> 070 { 071 try 072 { 073 runnable.run(); 074 } 075 catch ( RuntimeException | Error e ) 076 { 077 error.compareAndSet( null, e ); 078 throw e; 079 } 080 finally 081 { 082 counter.decrementAndGet(); 083 LockSupport.unpark( thread ); 084 } 085 }; 086 } 087 088 /** 089 * Causes the current thread to wait until all previously {@link #wrap(Runnable) wrapped} runnables have terminated 090 * and potentially re-throws an uncaught {@link RuntimeException} or {@link Error} from any of the runnables. In 091 * case multiple runnables encountered uncaught errors, one error is arbitrarily selected. <em>Note:</em> This 092 * method must be called from the same thread that created this error forwarder instance. 093 */ 094 public void await() 095 { 096 awaitTerminationOfAllRunnables(); 097 098 Throwable error = this.error.get(); 099 if ( error != null ) 100 { 101 if ( error instanceof RuntimeException ) 102 { 103 throw (RuntimeException) error; 104 } 105 else if ( error instanceof ThreadDeath ) 106 { 107 throw new IllegalStateException( error ); 108 } 109 else if ( error instanceof Error ) 110 { 111 throw (Error) error; 112 } 113 throw new IllegalStateException( error ); 114 } 115 } 116 117 private void awaitTerminationOfAllRunnables() 118 { 119 if ( !thread.equals( Thread.currentThread() ) ) 120 { 121 throw new IllegalStateException( "wrong caller thread, expected " + thread + " and not " 122 + Thread.currentThread() ); 123 } 124 125 boolean interrupted = false; 126 127 while ( counter.get() > 0 ) 128 { 129 LockSupport.park(); 130 131 if ( Thread.interrupted() ) 132 { 133 interrupted = true; 134 } 135 } 136 137 if ( interrupted ) 138 { 139 Thread.currentThread().interrupt(); 140 } 141 } 142 143}