org.astrogrid.samp

Class ShutdownManager

java.lang.Object

org.astrogrid.samp.ShutdownManager

public class ShutdownManager
extends Object

Handles ordered running of cleanup processes at JVM shutdown. This is a singleton class, use getInstance().

Since:

12 Oct 2012

Author:

Sylvain Lafrasse, Mark Taylor

Field Summary

Fields

Modifier and Type	Field and Description
static int	CLIENT_SEQUENCE Shutdown sequence value for client hooks.
static int	HUB_SEQUENCE Shutdown sequence value for hub hooks.
static int	PREPARE_SEQUENCE Shutdown sequence for preparatory hooks.

Method Summary

Modifier and Type	Method and Description
static void	forceLog(Logger logger, Level level, String msg, Throwable error) Writes a log-like message directly to standard error if it has an appropriate level.
static ShutdownManager	getInstance() Returns sole instance of this class.
void	registerHook(Object key, int iseq, Runnable runnable) Register a runnable to be run on shutdown with a given key and sequence.
void	unregisterHook(Object key) Unregisters a key earlier registered using registerHook(java.lang.Object, int, java.lang.Runnable).

Methods inherited from class java.lang.Object

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

Field Detail

PREPARE_SEQUENCE

public static final int PREPARE_SEQUENCE

Shutdown sequence for preparatory hooks.

See Also:

Constant Field Values

CLIENT_SEQUENCE

public static final int CLIENT_SEQUENCE

Shutdown sequence value for client hooks.

See Also:

Constant Field Values

HUB_SEQUENCE

public static final int HUB_SEQUENCE

Shutdown sequence value for hub hooks.

See Also:

Constant Field Values

Method Detail

registerHook

public void registerHook(Object key,
                         int iseq,
                         Runnable runnable)

Register a runnable to be run on shutdown with a given key and sequence. Items with a smaller value of iseq are run earlier at shutdown. Suitable sequence values are given by HUB_SEQUENCE and CLIENT_SEQUENCE. The key is kept in a WeakHashMap, so if it is GC'd, the runnable will never execute.

Parameters:

key - key which can be used to unregister the hook later

iseq - value indicating position in shutdown sequence

runnable - to be run on shutdown

unregisterHook

public void unregisterHook(Object key)

Unregisters a key earlier registered using registerHook(java.lang.Object, int, java.lang.Runnable).

Parameters:

key - registration key

getInstance

public static ShutdownManager getInstance()

Returns sole instance of this class.

Returns:

instance

forceLog

public static void forceLog(Logger logger,
                            Level level,
                            String msg,
                            Throwable error)

Writes a log-like message directly to standard error if it has an appropriate level. This method is only intended for use during the shutdown process, when the logging system may be turned off so that normal logging calls may get ignored (this behaviour is not as far as I know documented, but seems reliable in for example Oracle JRE1.5). There may be some good reason for logging services to be withdrawn during shutdown, so it's not clear that using this method is a good idea at all even apart from bypassing the logging system; therefore use it sparingly.

Parameters:

logger - logger

level - level of message to log

msg - text of logging message

error - associated throwable if any; may be null