net.openhft.chronicle.core.shutdown

Class Hooklet

java.lang.Object

net.openhft.chronicle.core.shutdown.Hooklet

All Implemented Interfaces:

Comparable<Hooklet>

public abstract class Hooklet
extends Object
implements Comparable<Hooklet>

Unit of work that can be registered with PriorityHook.

Implementations should be effectively immutable. Registration may occur from many threads but each hooklet is executed sequentially by the shutdown thread.

Allocate unique priorities in the range 0-100. Smaller values execute first and should be used for higher-level components.

Constructor Summary

Constructors

Constructor and Description
Hooklet()

Method Summary

Modifier and Type	Method and Description
int	compareTo(@NotNull Hooklet other) Orders hooklets by priority then identity.
boolean	equals(Object obj)
int	hashCode()
protected Object	identity() Hooks are only called once but may be registered multiple times.
static Hooklet	of(int priority, Runnable hook) Accepts callback and priority to produce shutdown hook object.
abstract void	onShutdown() Callback invoked by the shutdown thread.
abstract int	priority() Hooks with lesser priority will be called before hooks with greater priority.
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

Hooklet

public Hooklet()

Method Detail

onShutdown

public abstract void onShutdown()

Callback invoked by the shutdown thread. Implementations should return quickly and avoid long blocking operations.

priority

public abstract int priority()

Hooks with lesser priority will be called before hooks with greater priority.

It is advised to allocate an unique priority in the range of 0-100. In general, more high level code needs to do its shutdown routines before lower level code. An example priority layout is given below:

0: Run before all hooks. For test/example use. 1-49: Release of network resources and stopping distributed activity. 50-89: Release of local resources and stopping data structures. 90-99 Cleanup of file system resources such as temporary directories. 100: Run after all hooks. For test/example use.

identity

protected Object identity()

Hooks are only called once but may be registered multiple times. To determine if hook is already present, an object returned by this method is compared.

The default implementation returns this instance's class and should usually be sufficient.

Returns:

object used to identify the hooklet

of

public static Hooklet of(int priority,
                         Runnable hook)

Accepts callback and priority to produce shutdown hook object.

Hook callback class is used to check for identity, see identity().

Parameters:

priority - value returned by priority()

hook - action to run on shutdown

Returns:

hooklet wrapping the given action

Throws:

NullPointerException - if hook is null

compareTo

public int compareTo(@NotNull
                     @NotNull Hooklet other)

Orders hooklets by priority then identity.

Specified by:

compareTo in interface Comparable<Hooklet>

Parameters:

other - hooklet to compare

Returns:

negative if this should run before other

equals

public boolean equals(Object obj)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object