net.sf.eBus.util

Class ShutdownHook

java.lang.Object

java.lang.Thread

net.sf.eBus.util.ShutdownHook

All Implemented Interfaces:

Runnable

public final class ShutdownHook
extends Thread

Provides a simple way for an console-based, Java application main thread to wait until the virtual machine terminates. If an application main method is solely responsible for setting up and tearing down the application and hands off control to another thread between the two, then the main thread must block until it is time to stop. This class is a Java shutdown hook, returning a CountDownLatch on which the main thread waits. This latch is decremented when the Java Runtime executes the shutdown hook. Since the latch is size one, CountDownLatch.await() will return.

This returned latch may be passed to other objects which can decrement the latch and so signal that the application is to terminate.

An example Java main method uses this class as follows:

   
 import java.util.concurrent.CountDownLatch;

 public static void main(final String args[])
 {
     // 1. Check the command line arguments.
     // 2. Initialize the application.
     // 3. Set up the shutdown hook.
     final CountDownLatch signal = ShutdownHook.addShutdownHook();

     // 4. Start application thread.
     // 5. Wait for the JVM to stop.
     try {
         signal.await();
     } catch (InterruptedException interrupt) {}

     // 6. Tear down the application.
 }
   
 

Author:

Charles Rapp

Nested Class Summary

Nested classes/interfaces inherited from class java.lang.Thread

Thread.State, Thread.UncaughtExceptionHandler

Field Summary

Fields inherited from class java.lang.Thread

MAX_PRIORITY, MIN_PRIORITY, NORM_PRIORITY

Method Summary

Modifier and Type	Method and Description
static CountDownLatch	addShutdownHook() Returns the signal used by the shutdown hook to notify the caller when the JVM is shutdown.
static void	removeShutdownHook() Unhooks the shutdown hook instance from the system runtime.
void	run() Decrements the signal which results in a return from CountDownLatch.await().

Methods inherited from class java.lang.Thread

activeCount, checkAccess, clone, countStackFrames, currentThread, destroy, dumpStack, enumerate, getAllStackTraces, getContextClassLoader, getDefaultUncaughtExceptionHandler, getId, getName, getPriority, getStackTrace, getState, getThreadGroup, getUncaughtExceptionHandler, holdsLock, interrupt, interrupted, isAlive, isDaemon, isInterrupted, join, join, join, resume, setContextClassLoader, setDaemon, setDefaultUncaughtExceptionHandler, setName, setPriority, setUncaughtExceptionHandler, sleep, sleep, start, stop, stop, suspend, toString, yield

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Method Detail

run

public void run()

Decrements the signal which results in a return from CountDownLatch.await().

Specified by:

run in interface Runnable

Overrides:

run in class Thread

addShutdownHook

public static CountDownLatch addShutdownHook()

Returns the signal used by the shutdown hook to notify the caller when the JVM is shutdown. If the shutdown hook does not exist, then creates it and adds it to the default system runtime. The count down latch size is one, which means that CountDownLatch.await() returns as soon as this latch is decremented.

Returns:

the shutdown hook signal.

removeShutdownHook

public static void removeShutdownHook()

Unhooks the shutdown hook instance from the system runtime.