投稿日： 2019年4月12日

【Eclipse】SpringBootデバッグ時に発生するSilentExitExceptionの原因と対処方法【spring-boot-devtools】

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1 EclipseにおけるSpringBootデバック時の謎のエラー
2 手順
- 2.1 Eclipseの設定変更
3 終わりに

EclipseにおけるSpringBootデバック時の謎のエラー

Eclipse環境でSpringBootのシステムを開発している場合、もちろんデバッグを行うと思うのですが、SilentExitException という、謎のエラーが発生すると思います。

/*
 * Copyright 2012-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.boot.devtools.restart;

import java.lang.Thread.UncaughtExceptionHandler;
import java.util.Arrays;

/**
 * {@link UncaughtExceptionHandler} decorator that allows a thread to exit silently.
 *
 * @author Phillip Webb
 * @author Andy Wilkinson
 */
class SilentExitExceptionHandler implements UncaughtExceptionHandler {

	private final UncaughtExceptionHandler delegate;

	SilentExitExceptionHandler(UncaughtExceptionHandler delegate) {
		this.delegate = delegate;
	}

	@Override
	public void uncaughtException(Thread thread, Throwable exception) {
		if (exception instanceof SilentExitException) {
			if (isJvmExiting(thread)) {
				preventNonZeroExitCode();
			}
			return;
		}
		if (this.delegate != null) {
			this.delegate.uncaughtException(thread, exception);
		}
	}

	private boolean isJvmExiting(Thread exceptionThread) {
		for (Thread thread : getAllThreads()) {
			if (thread != exceptionThread && thread.isAlive() && !thread.isDaemon()) {
				return false;
			}
		}
		return true;
	}

	protected Thread[] getAllThreads() {
		ThreadGroup rootThreadGroup = getRootThreadGroup();
		Thread[] threads = new Thread[32];
		int count = rootThreadGroup.enumerate(threads);
		while (count == threads.length) {
			threads = new Thread[threads.length * 2];
			count = rootThreadGroup.enumerate(threads);
		}
		return Arrays.copyOf(threads, count);
	}

	private ThreadGroup getRootThreadGroup() {
		ThreadGroup candidate = Thread.currentThread().getThreadGroup();
		while (candidate.getParent() != null) {
			candidate = candidate.getParent();
		}
		return candidate;
	}

	protected void preventNonZeroExitCode() {
		System.exit(0);
	}

	public static void setup(Thread thread) {
		UncaughtExceptionHandler handler = thread.getUncaughtExceptionHandler();
		if (!(handler instanceof SilentExitExceptionHandler)) {
			handler = new SilentExitExceptionHandler(handler);
			thread.setUncaughtExceptionHandler(handler);
		}
	}

	public static void exitCurrentThread() {
		throw new SilentExitException(); //　ここでエラーが発生
	}

	private static class SilentExitException extends RuntimeException {

	}

}

* Licensed under the Apache License, Version 2.0 (the "License");

* you may not use this file except in compliance with the License.

* You may obtain a copy of the License at

* http://www.apache.org/licenses/LICENSE-2.0

* Unless required by applicable law or agreed to in writing, software

* distributed under the License is distributed on an "AS IS" BASIS,

* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

* See the License for the specific language governing permissions and

* limitations under the License.

package org.springframework.boot.devtools.restart;

import java.lang.Thread.UncaughtExceptionHandler;

import java.util.Arrays;

/**

* {@link UncaughtExceptionHandler} decorator that allows a thread to exit silently.

* @author Phillip Webb

* @author Andy Wilkinson

class SilentExitExceptionHandler implements UncaughtExceptionHandler {

private final UncaughtExceptionHandler delegate;

SilentExitExceptionHandler(UncaughtExceptionHandler delegate) {

this.delegate = delegate;

}

@Override

public void uncaughtException(Thread thread, Throwable exception) {

if (exception instanceof SilentExitException) {

if (isJvmExiting(thread)) {

preventNonZeroExitCode();

}

return;

}

if (this.delegate != null) {

this.delegate.uncaughtException(thread, exception);

}

private boolean isJvmExiting(Thread exceptionThread) {

for (Thread thread : getAllThreads()) {

if (thread != exceptionThread && thread.isAlive() && !thread.isDaemon()) {

return false;

}

return true;

}

protected Thread[] getAllThreads() {

ThreadGroup rootThreadGroup = getRootThreadGroup();

Thread[] threads = new Thread[32];

int count = rootThreadGroup.enumerate(threads);

while (count == threads.length) {

threads = new Thread[threads.length * 2];

count = rootThreadGroup.enumerate(threads);

}

return Arrays.copyOf(threads, count);

}

private ThreadGroup getRootThreadGroup() {

ThreadGroup candidate = Thread.currentThread().getThreadGroup();

while (candidate.getParent() != null) {

candidate = candidate.getParent();

}

return candidate;

}

protected void preventNonZeroExitCode() {

System.exit(0);

}

public static void setup(Thread thread) {

UncaughtExceptionHandler handler = thread.getUncaughtExceptionHandler();

if (!(handler instanceof SilentExitExceptionHandler)) {

handler = new SilentExitExceptionHandler(handler);

thread.setUncaughtExceptionHandler(handler);

}

public static void exitCurrentThread() {

throw new SilentExitException(); //　ここでエラーが発生

}

private static class SilentExitException extends RuntimeException {

}

ブレークポイントを貼っているわけでもないのに、毎回デバッグ起動時に引っかかるので、正直とても厄介ですorz

実はこれ、spring-boot-devtoolsのバグのようです><

This is unfortunately a know issue with the new spring-boot-devtools module (see https://github.com/spring-projects/spring-boot/issues/3100). We use this trick to kill the main thread so that we can replace it with a re-loadable version. So far I’ve not found a way to prevent the debug breakpoint from triggering.

For now, you can toggle the “suspend execution on uncaught exceptions” checkbox in Java -> Debug preferences to prevent it from happening.java – Breakpoint at “throw new SilentExitException()” in Eclipse + Spring Boot – Stack Overflow

しかし安心してください。
Eclipseの設定を変えるだけでエラーが発生する事無くなるので、今回はその手順をご紹介致します。