java.nio.channels.spi
Class AbstractSelectableChannel

java.lang.Object
  java.nio.channels.spi.AbstractInterruptibleChannel
      java.nio.channels.SelectableChannel
          java.nio.channels.spi.AbstractSelectableChannel

All Implemented Interfaces:

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

Author:

Mark Reinhold, Mike McCloskey, JSR-51 Expert Group

Nested Class Summary

Nested classes inherited from class java.nio.channels.spi.AbstractInterruptibleChannel

Field Summary

(package private) boolean	blocking
private int	keyCount
private Object	keyLock
private SelectionKey[]	keys
private SelectorProvider	provider
private Object	regLock

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

Constructor Summary

protected

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

Method Summary

private void	addKey(SelectionKey k)
Object	blockingLock() Retrieves the object upon which the configureBlocking and register methods synchronize.
SelectableChannel	configureBlocking(boolean block) Adjusts this channel's blocking mode.
private SelectionKey	findKey(Selector sel)
private boolean	haveValidKeys()
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.
(package private) void	removeKey(SelectionKey k)

Methods inherited from class java.nio.channels.SelectableChannel

register, validOps

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

begin, blockedOn, 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

Field Detail

provider

private final SelectorProvider provider

keys

private SelectionKey[] keys

keyCount

private int keyCount

keyLock

private final Object keyLock

regLock

private final Object regLock

blocking

boolean blocking

Constructor Detail

AbstractSelectableChannel

protected AbstractSelectableChannel(SelectorProvider provider)

Initializes a new instance of this class.

Method Detail

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

addKey

private void addKey(SelectionKey k)

findKey

private SelectionKey findKey(Selector sel)

removeKey

void removeKey(SelectionKey k)

haveValidKeys

private boolean haveValidKeys()

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

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:

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

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:

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.

Throws:

IOException - If an I/O error occurs