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 032@ElementTypesAreNonnullByDefault 033public final class UncaughtExceptionHandlers { 034 private UncaughtExceptionHandlers() {} 035 036 /** 037 * Returns an exception handler that exits the system. This is particularly useful for the main 038 * thread, which may start up other, non-daemon threads, but fail to fully initialize the 039 * application successfully. 040 * 041 * <p>Example usage: 042 * 043 * <pre> 044 * public static void main(String[] args) { 045 * Thread.currentThread().setUncaughtExceptionHandler(UncaughtExceptionHandlers.systemExit()); 046 * ... 047 * </pre> 048 * 049 * <p>The returned handler logs any exception at severity {@code SEVERE} and then shuts down the 050 * process with an exit status of 1, indicating abnormal termination. 051 */ 052 public static UncaughtExceptionHandler systemExit() { 053 return new Exiter(Runtime.getRuntime()); 054 } 055 056 @VisibleForTesting 057 static final class Exiter implements UncaughtExceptionHandler { 058 private static final Logger logger = Logger.getLogger(Exiter.class.getName()); 059 060 private final Runtime runtime; 061 062 Exiter(Runtime runtime) { 063 this.runtime = runtime; 064 } 065 066 @Override 067 public void uncaughtException(Thread t, Throwable e) { 068 try { 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}