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.J2ktIncompatible; 021import com.google.common.annotations.VisibleForTesting; 022import java.lang.Thread.UncaughtExceptionHandler; 023import java.util.Locale; 024 025/** 026 * Factories for {@link UncaughtExceptionHandler} instances. 027 * 028 * @author Gregory Kick 029 * @since 8.0 030 */ 031@J2ktIncompatible 032@GwtIncompatible 033@ElementTypesAreNonnullByDefault 034public final class UncaughtExceptionHandlers { 035 private UncaughtExceptionHandlers() {} 036 037 /** 038 * Returns an exception handler that exits the system. This is particularly useful for the main 039 * thread, which may start up other, non-daemon threads, but fail to fully initialize the 040 * application successfully. 041 * 042 * <p>Example usage: 043 * 044 * <pre> 045 * public static void main(String[] args) { 046 * Thread.currentThread().setUncaughtExceptionHandler(UncaughtExceptionHandlers.systemExit()); 047 * ... 048 * </pre> 049 * 050 * <p>The returned handler logs any exception at severity {@code SEVERE} and then shuts down the 051 * process with an exit status of 1, indicating abnormal termination. 052 */ 053 public static UncaughtExceptionHandler systemExit() { 054 return new Exiter(Runtime.getRuntime()); 055 } 056 057 @VisibleForTesting 058 static final class Exiter implements UncaughtExceptionHandler { 059 private static final LazyLogger logger = new LazyLogger(Exiter.class); 060 061 private final Runtime runtime; 062 063 Exiter(Runtime runtime) { 064 this.runtime = runtime; 065 } 066 067 @Override 068 public void uncaughtException(Thread t, Throwable e) { 069 try { 070 logger 071 .get() 072 .log( 073 SEVERE, 074 String.format(Locale.ROOT, "Caught an exception in %s. Shutting down.", t), 075 e); 076 } catch (Throwable errorInLogging) { // sneaky checked exception 077 // If logging fails, e.g. due to missing memory, at least try to log the 078 // message and the cause for the failed logging. 079 System.err.println(e.getMessage()); 080 System.err.println(errorInLogging.getMessage()); 081 } finally { 082 runtime.exit(1); 083 } 084 } 085 } 086}