com.github.triceo.robozonky.app.ShutdownEnabler Maven / Gradle / Ivy
/*
* Copyright 2017 Lukáš Petrovický
*
* 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 com.github.triceo.robozonky.app;
import java.util.Optional;
import java.util.concurrent.Semaphore;
import java.util.function.Consumer;
/**
* Makes sure that when Ctrl+C is pressed in daemon-mode, the app cleanly shuts down.
*/
public class ShutdownEnabler implements ShutdownHook.Handler {
public static final Semaphore DAEMON_ALLOWED_TO_TERMINATE = new Semaphore(1);
@Override
public Optional> get() {
// will be acquired immediately after RoboZonky startup
ShutdownEnabler.DAEMON_ALLOWED_TO_TERMINATE.acquireUninterruptibly();
return Optional.of((returnCode -> {
/*
* when the code gets here during shutdown, control is handed over to the daemon, which is already
* waiting to acquire; application will relinquish control and the JVM will shut down.
*/
ShutdownEnabler.DAEMON_ALLOWED_TO_TERMINATE.release();
}));
}
}