com.izforge.izpack.util.Housekeeper Maven / Gradle / Ivy
/*
* IzPack - Copyright 2001-2008 Julien Ponge, All Rights Reserved.
*
* http://izpack.org/
* http://izpack.codehaus.org/
*
* Copyright 2002 Elmar Grom
*
* 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.izforge.izpack.util;
import java.util.Vector;
/*---------------------------------------------------------------------------*/
/**
* This class performs housekeeping and cleanup tasks. There can only be one instance of
* Housekeeper per Java runtime, therefore this class is implemented as a
* 'Singleton'.
*
* It is VERY important to perform pre-shutdown cleanup operations through this class. Do NOT rely
* on operations like deleteOnExit() shutdown hooks or finalize()for
* cleanup. Because shutDown() uses System.exit() to terminate, these
* methods will not work at all or will not work reliably.
*
* @author Elmar Grom
* @version 0.0.1 / 2/9/02
*/
/*---------------------------------------------------------------------------*/
public class Housekeeper
{
// ------------------------------------------------------------------------
// Variable Declarations
// ------------------------------------------------------------------------
private static Housekeeper me = null;
private Vector cleanupClients = new Vector();
/*--------------------------------------------------------------------------*/
/**
* This class is implemented as a 'Singleton'. Therefore the constructor is private to prevent
* instantiation of this class. Use getInstance() to obtain an instance for use.
*
*
* For more information about the 'Singleton' pattern I highly recommend the book Design
* Patterns by Gamma, Helm, Johnson and Vlissides ISBN 0-201-63361-2.
*/
/*--------------------------------------------------------------------------*/
private Housekeeper()
{
}
/*--------------------------------------------------------------------------*/
/**
* Returns an instance of Housekeeper to use.
*
* @return an instance of Housekeeper.
*/
/*--------------------------------------------------------------------------*/
public static Housekeeper getInstance()
{
if (me == null)
{
me = new Housekeeper();
}
return (me);
}
/*--------------------------------------------------------------------------*/
/**
* Use to register objects that need to perform cleanup operations before the application shuts
* down.
*
* @param client reference of to an object that needs to perform cleanup operations.
*/
/*--------------------------------------------------------------------------*/
public void registerForCleanup(CleanupClient client)
{
cleanupClients.add(client);
}
/*--------------------------------------------------------------------------*/
/**
* This methods shuts the application down. First, it will call all clients that have registered
* for cleanup operations. Once this has been accomplished, the application will be forceably
* terminated.
*
* THIS METHOD DOES NOT RETURN!
*
* @param exitCode the exit code that should be returned to the calling process.
*/
/*--------------------------------------------------------------------------*/
public void shutDown(int exitCode)
{
for (int i = 0; i < cleanupClients.size(); i++)
{
try
{
(cleanupClients.elementAt(i)).cleanUp();
}
catch (Throwable exception)
{
// At this point we can not afford to treat exceptions. Cleanup
// that
// can not be completed might unfortunately leave some garbage
// behind.
// If we have a logging module, any exceptions received here
// should
// be written to the log.
}
}
System.exit(exitCode);
}
}
/*---------------------------------------------------------------------------*/