Class AbstractSelectableChannel

All Implemented Interfaces:
Closeable, AutoCloseable, Channel, InterruptibleChannel
Direct Known Subclasses:
DatagramChannel, Pipe.SinkChannel, Pipe.SourceChannel, ServerSocketChannel, SocketChannel 

public abstract class AbstractSelectableChannel
extends SelectableChannel

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.

Since:
1.4

Constructors

Modifier Constructor and Description
protected AbstractSelectableChannel(SelectorProvider provider)

Initializes a new instance of this class.

Methods

Modifier and Type Method and Description
Object blockingLock()

Retrieves the object upon which the configureBlocking and register methods synchronize.
SelectableChannel configureBlocking(boolean block)

Adjusts this channel's blocking mode.
protected void implCloseChannel()

Closes this channel.
protected abstract void implCloseSelectableChannel()

Closes this selectable channel.
protected abstract void implConfigureBlocking(boolean block)

Adjusts this channel's blocking mode.
boolean isBlocking()

Tells whether or not every I/O operation on this channel will block until it completes.
boolean isRegistered()

Tells whether or not this channel is currently registered with any selectors.
SelectionKey keyFor(Selector sel)

Retrieves the key representing the channel's registration with the given selector.
SelectorProvider provider()

Returns the provider that created this channel.
SelectionKey register(Selector sel, int ops, Object att)

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

Methods inherited from class java.nio.channels.SelectableChannel

register, validOps

Methods inherited from class java.nio.channels.spi.AbstractInterruptibleChannel

begin, close, end, isOpen

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.nio.channels.Channel

close, isOpen

Constructors

AbstractSelectableChannel

protected AbstractSelectableChannel(SelectorProvider provider)

Initializes a new instance of this class.

Parameters:
provider - The provider that created this channel

Methods

provider

public final SelectorProvider provider()

Returns the provider that created this channel.

Specified by:
provider in class SelectableChannel
Returns:
The provider that created this channel

isRegistered

public final boolean isRegistered()

Description copied from class: SelectableChannel

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.

Specified by:
isRegistered in class SelectableChannel
Returns:
true if, and only if, this channel is registered

keyFor

public final SelectionKey keyFor(Selector sel)

Description copied from class: SelectableChannel

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

Specified by:
keyFor in class SelectableChannel
Parameters:
sel - The selector
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

register

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

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.

Specified by:
register in class SelectableChannel
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
Throws:
ClosedSelectorException - If the selector is closed
IllegalBlockingModeException - If this channel is in blocking mode
IllegalSelectorException - If this channel was not created by the same provider as the given selector
CancelledKeyException - If this channel is currently registered with the given selector but the corresponding key has already been cancelled
IllegalArgumentException - If a bit in the ops set does not correspond to an operation that is supported by this channel, that is, if set & ~validOps() != 0
ClosedChannelException - If this channel is closed

implCloseChannel

protected final void implCloseChannel()
                               throws IOException

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.

Specified by:
implCloseChannel in class AbstractInterruptibleChannel
Throws:
IOException - If an I/O error occurs while closing the channel

implCloseSelectableChannel

protected abstract void implCloseSelectableChannel()
                                            throws IOException

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 - If an I/O error occurs

isBlocking

public final boolean isBlocking()

Description copied from class: SelectableChannel

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.

Specified by:
isBlocking in class SelectableChannel
Returns:
true if, and only if, this channel is in blocking mode

blockingLock

public final Object blockingLock()

Description copied from class: SelectableChannel

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.

Specified by:
blockingLock in class SelectableChannel
Returns:
The blocking-mode lock object

configureBlocking

public final SelectableChannel configureBlocking(boolean block)
                                          throws IOException

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.

Specified by:
configureBlocking in class SelectableChannel
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:
ClosedChannelException - If this channel is closed
IOException - If an I/O error occurs

implConfigureBlocking

protected abstract void implConfigureBlocking(boolean block)
                                       throws IOException

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 - If true then this channel will be placed in blocking mode; if false then it will be placed non-blocking mode
Throws:
IOException - If an I/O error occurs

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https://docs.oracle.com/javase/8/docs/api/java/nio/channels/spi/AbstractSelectableChannel.html