ShutdownManager

java.lang.Object
- org.astrogrid.samp.ShutdownManager

```
public class ShutdownManager
extends java.lang.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

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

private static class ShutdownManager.Hook
Aggregates a runnable and an associated sequence value.

Nested Classes
Modifier and Type	Class and Description
`private static class`	`ShutdownManager.Hook` Aggregates a runnable and an associated sequence value.

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`CLIENT_SEQUENCE` Shutdown sequence value for client hooks.
`private java.util.WeakHashMap`	`hookMap_` Maps Objects to Hooks.
`static int`	`HUB_SEQUENCE` Shutdown sequence value for hub hooks.
`private static ShutdownManager`	`instance_`
`private static java.util.logging.Logger`	`logger_`
`static int`	`PREPARE_SEQUENCE` Shutdown sequence for preparatory hooks.

Constructor Summary

Constructors
Modifier Constructor and Description

private ShutdownManager()
Private constructor prevents instantiation.

Constructors
Modifier	Constructor and Description
`private`	`ShutdownManager()` Private constructor prevents instantiation.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`private void`	`doCleanup()` Invoked on shutdown by runtime.
`static void`	`forceLog(java.util.logging.Logger logger, java.util.logging.Level level, java.lang.String msg, java.lang.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(java.lang.Object key, int iseq, java.lang.Runnable runnable)` Register a runnable to be run on shutdown with a given key and sequence.
`void`	`unregisterHook(java.lang.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
  - instance_
```
private static final ShutdownManager instance_
```
  - logger_
```
private static final java.util.logging.Logger logger_
```
  - hookMap_
```
private final java.util.WeakHashMap hookMap_
```
    Maps Objects to Hooks.
- Constructor Detail
  - ShutdownManager
```
private ShutdownManager()
```
    Private constructor prevents instantiation.
- Method Detail
  - registerHook
```
public void registerHook(java.lang.Object key,
                         int iseq,
                         java.lang.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(java.lang.Object key)
```
    Unregisters a key earlier registered using registerHook(java.lang.Object, int, java.lang.Runnable).
    
    Parameters:
    
    key - registration key
  - doCleanup
```
private void doCleanup()
```
    Invoked on shutdown by runtime.
  - getInstance
```
public static ShutdownManager getInstance()
```
    Returns sole instance of this class.
    
    Returns:
    
    instance
  - forceLog
```
public static void forceLog(java.util.logging.Logger logger,
                            java.util.logging.Level level,
                            java.lang.String msg,
                            java.lang.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

Class ShutdownManager

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

PREPARE_SEQUENCE

CLIENT_SEQUENCE

HUB_SEQUENCE

instance_

logger_

hookMap_

Constructor Detail

ShutdownManager

Method Detail

registerHook

unregisterHook

doCleanup

getInstance

forceLog