1 /* 2 * Copyright (C) 2010 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.common.util.concurrent; 18 19 import static java.util.logging.Level.SEVERE; 20 21 import com.google.common.annotations.VisibleForTesting; 22 23 import java.lang.Thread.UncaughtExceptionHandler; 24 import java.util.logging.Logger; 25 26 /** 27 * Factories for {@link UncaughtExceptionHandler} instances. 28 * 29 * @author Gregory Kick 30 * @since 8.0 31 */ 32 public final class UncaughtExceptionHandlers { UncaughtExceptionHandlers()33 private UncaughtExceptionHandlers() {} 34 35 /** 36 * Returns an exception handler that exits the system. This is particularly useful for the main 37 * thread, which may start up other, non-daemon threads, but fail to fully initialize the 38 * application successfully. 39 * 40 * <p>Example usage: 41 * <pre>public static void main(String[] args) { 42 * Thread.currentThread().setUncaughtExceptionHandler(UncaughtExceptionHandlers.systemExit()); 43 * ... 44 * </pre> 45 * 46 * <p>The returned handler logs any exception at severity {@code SEVERE} and then shuts down the 47 * process with an exit status of 1, indicating abnormal termination. 48 */ systemExit()49 public static UncaughtExceptionHandler systemExit() { 50 return new Exiter(Runtime.getRuntime()); 51 } 52 53 @VisibleForTesting static final class Exiter implements UncaughtExceptionHandler { 54 private static final Logger logger = Logger.getLogger(Exiter.class.getName()); 55 56 private final Runtime runtime; 57 Exiter(Runtime runtime)58 Exiter(Runtime runtime) { 59 this.runtime = runtime; 60 } 61 uncaughtException(Thread t, Throwable e)62 @Override public void uncaughtException(Thread t, Throwable e) { 63 try { 64 // cannot use FormattingLogger due to a dependency loop 65 logger.log(SEVERE, String.format("Caught an exception in %s. Shutting down.", t), e); 66 } catch (Throwable errorInLogging) { 67 // If logging fails, e.g. due to missing memory, at least try to log the 68 // message and the cause for the failed logging. 69 System.err.println(e.getMessage()); 70 System.err.println(errorInLogging.getMessage()); 71 } finally { 72 runtime.exit(1); 73 } 74 } 75 } 76 } 77