AbstractSelectableChannel

public abstract class AbstractSelectableChannel extends SelectableChannel
Known Direct Subclasses

Base implementation class for selectable channels.

This class defines methods that handle the mechanics of channel registration, deregistration, and closing. It maintains the current blocking mode of this channel as well as its current set of selection keys. It performs all of the synchronization required to implement the SelectableChannel specification. Implementations of the abstract protected methods defined in this class need not synchronize against other threads that might be engaged in the same operations.

Protected Constructor Summary

AbstractSelectableChannel(SelectorProvider provider)
Initializes a new instance of this class.

Public Method Summary

final Object
blockingLock()
Retrieves the object upon which the configureBlocking and register methods synchronize.
final SelectableChannel
configureBlocking(boolean block)
Adjusts this channel's blocking mode.
final boolean
isBlocking()
Tells whether or not every I/O operation on this channel will block until it completes.
final boolean
isRegistered()
Tells whether or not this channel is currently registered with any selectors.
final SelectionKey
keyFor(Selector sel)
Retrieves the key representing the channel's registration with the given selector.
final SelectorProvider
provider()
Returns the provider that created this channel.
final SelectionKey
register(Selector sel, int ops, Object att)
Registers this channel with the given selector, returning a selection key.

Protected Method Summary

final void
implCloseChannel()
Closes this channel.
abstract void
implCloseSelectableChannel()
Closes this selectable channel.
abstract void
implConfigureBlocking(boolean block)
Adjusts this channel's blocking mode.

Inherited Method Summary

Protected Constructors

protected AbstractSelectableChannel (SelectorProvider provider)

Initializes a new instance of this class.

Parameters
provider

Public Methods

public final Object blockingLock ()

Retrieves the object upon which the configureBlocking and register methods synchronize. This is often useful in the implementation of adaptors that require a specific blocking mode to be maintained for a short period of time.

Returns
  • The blocking-mode lock object

public final SelectableChannel configureBlocking (boolean block)

Adjusts this channel's blocking mode.

If the given blocking mode is different from the current blocking mode then this method invokes the implConfigureBlocking method, while holding the appropriate locks, in order to change the mode.

Parameters
block If true then this channel will be placed in blocking mode; if false then it will be placed non-blocking mode
Returns
  • This selectable channel
Throws
IOException

public final boolean isBlocking ()

Tells whether or not every I/O operation on this channel will block until it completes. A newly-created channel is always in blocking mode.

If this channel is closed then the value returned by this method is not specified.

Returns
  • true if, and only if, this channel is in blocking mode

public final boolean isRegistered ()

Tells whether or not this channel is currently registered with any selectors. A newly-created channel is not registered.

Due to the inherent delay between key cancellation and channel deregistration, a channel may remain registered for some time after all of its keys have been cancelled. A channel may also remain registered for some time after it is closed.

Returns
  • true if, and only if, this channel is registered

public final SelectionKey keyFor (Selector sel)

Retrieves the key representing the channel's registration with the given selector.

Parameters
sel
Returns
  • The key returned when this channel was last registered with the given selector, or null if this channel is not currently registered with that selector

public final SelectorProvider provider ()

Returns the provider that created this channel.

Returns
  • The provider that created this channel

public final SelectionKey register (Selector sel, int ops, Object att)

Registers this channel with the given selector, returning a selection key.

This method first verifies that this channel is open and that the given initial interest set is valid.

If this channel is already registered with the given selector then the selection key representing that registration is returned after setting its interest set to the given value.

Otherwise this channel has not yet been registered with the given selector, so the register method of the selector is invoked while holding the appropriate locks. The resulting key is added to this channel's key set before being returned.

Parameters
sel The selector with which this channel is to be registered
ops The interest set for the resulting key
att The attachment for the resulting key; may be null
Returns
  • A key representing the registration of this channel with the given selector

Protected Methods

protected final void implCloseChannel ()

Closes this channel.

This method, which is specified in the AbstractInterruptibleChannel class and is invoked by the close method, in turn invokes the implCloseSelectableChannel method in order to perform the actual work of closing this channel. It then cancels all of this channel's keys.

Throws
IOException

protected abstract void implCloseSelectableChannel ()

Closes this selectable channel.

This method is invoked by the close method in order to perform the actual work of closing the channel. This method is only invoked if the channel has not yet been closed, and it is never invoked more than once.

An implementation of this method must arrange for any other thread that is blocked in an I/O operation upon this channel to return immediately, either by throwing an exception or by returning normally.

Throws
IOException

protected abstract void implConfigureBlocking (boolean block)

Adjusts this channel's blocking mode.

This method is invoked by the configureBlocking method in order to perform the actual work of changing the blocking mode. This method is only invoked if the new mode is different from the current mode.

Parameters
block
Throws
IOException If an I/O error occurs