001/* 002 * Copyright (C) 2010 The Guava Authors 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except 005 * in compliance with the License. You may obtain a copy of the License at 006 * 007 * http://www.apache.org/licenses/LICENSE-2.0 008 * 009 * Unless required by applicable law or agreed to in writing, software distributed under the License 010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express 011 * or implied. See the License for the specific language governing permissions and limitations under 012 * the License. 013 */ 014 015package com.google.common.util.concurrent; 016 017import static java.util.logging.Level.SEVERE; 018 019import com.google.common.annotations.GwtIncompatible; 020import com.google.common.annotations.VisibleForTesting; 021import java.lang.Thread.UncaughtExceptionHandler; 022import java.util.Locale; 023import java.util.logging.Logger; 024 025/** 026 * Factories for {@link UncaughtExceptionHandler} instances. 027 * 028 * @author Gregory Kick 029 * @since 8.0 030 */ 031@GwtIncompatible 032public final class UncaughtExceptionHandlers { 033 private UncaughtExceptionHandlers() {} 034 035 /** 036 * Returns an exception handler that exits the system. This is particularly useful for the main 037 * thread, which may start up other, non-daemon threads, but fail to fully initialize the 038 * application successfully. 039 * 040 * <p>Example usage: 041 * 042 * <pre> 043 * public static void main(String[] args) { 044 * Thread.currentThread().setUncaughtExceptionHandler(UncaughtExceptionHandlers.systemExit()); 045 * ... 046 * </pre> 047 * 048 * <p>The returned handler logs any exception at severity {@code SEVERE} and then shuts down the 049 * process with an exit status of 1, indicating abnormal termination. 050 */ 051 public static UncaughtExceptionHandler systemExit() { 052 return new Exiter(Runtime.getRuntime()); 053 } 054 055 @VisibleForTesting 056 static final class Exiter implements UncaughtExceptionHandler { 057 private static final Logger logger = Logger.getLogger(Exiter.class.getName()); 058 059 private final Runtime runtime; 060 061 Exiter(Runtime runtime) { 062 this.runtime = runtime; 063 } 064 065 @Override 066 public void uncaughtException(Thread t, Throwable e) { 067 try { 068 // cannot use FormattingLogger due to a dependency loop 069 logger.log( 070 SEVERE, String.format(Locale.ROOT, "Caught an exception in %s. Shutting down.", t), e); 071 } catch (Throwable errorInLogging) { 072 // If logging fails, e.g. due to missing memory, at least try to log the 073 // message and the cause for the failed logging. 074 System.err.println(e.getMessage()); 075 System.err.println(errorInLogging.getMessage()); 076 } finally { 077 runtime.exit(1); 078 } 079 } 080 } 081}