1 /*
2 * Copyright (C) 2010 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
5 * in compliance with the License. You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software distributed under the License
10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
11 * or implied. See the License for the specific language governing permissions and limitations under
12 * the License.
13 */
14
15 package com.google.common.util.concurrent;
16
17 import static java.util.logging.Level.SEVERE;
18
19 import com.google.common.annotations.GwtIncompatible;
20 import com.google.common.annotations.VisibleForTesting;
21 import java.lang.Thread.UncaughtExceptionHandler;
22 import java.util.Locale;
23 import java.util.logging.Logger;
24
25 /**
26 * Factories for {@link UncaughtExceptionHandler} instances.
27 *
28 * @author Gregory Kick
29 * @since 8.0
30 */
31 @GwtIncompatible
32 @ElementTypesAreNonnullByDefault
33 public final class UncaughtExceptionHandlers {
34 private UncaughtExceptionHandlers() {}
35
36 /**
37 * Returns an exception handler that exits the system. This is particularly useful for the main
38 * thread, which may start up other, non-daemon threads, but fail to fully initialize the
39 * application successfully.
40 *
41 * <p>Example usage:
42 *
43 * <pre>
44 * public static void main(String[] args) {
45 * Thread.currentThread().setUncaughtExceptionHandler(UncaughtExceptionHandlers.systemExit());
46 * ...
47 * </pre>
48 *
49 * <p>The returned handler logs any exception at severity {@code SEVERE} and then shuts down the
50 * process with an exit status of 1, indicating abnormal termination.
51 */
52 public static UncaughtExceptionHandler systemExit() {
53 return new Exiter(Runtime.getRuntime());
54 }
55
56 @VisibleForTesting
57 static final class Exiter implements UncaughtExceptionHandler {
58 private static final Logger logger = Logger.getLogger(Exiter.class.getName());
59
60 private final Runtime runtime;
61
62 Exiter(Runtime runtime) {
63 this.runtime = runtime;
64 }
65
66 @Override
67 public void uncaughtException(Thread t, Throwable e) {
68 try {
69 logger.log(
70 SEVERE, String.format(Locale.ROOT, "Caught an exception in %s. Shutting down.", t), e);
71 } catch (Throwable errorInLogging) {
72 // If logging fails, e.g. due to missing memory, at least try to log the
73 // message and the cause for the failed logging.
74 System.err.println(e.getMessage());
75 System.err.println(errorInLogging.getMessage());
76 } finally {
77 runtime.exit(1);
78 }
79 }
80 }
81 }