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| java.lang.Object
 java.nio.channels.spi.AbstractInterruptibleChannel
java.nio.channels.SelectableChannel
All known Subclasses: java.nio.channels.spi.AbstractSelectableChannel,
| SelectableChannel | | abstract public class SelectableChannel extends AbstractInterruptibleChannel implements Channel(Code) | | A channel that can be multiplexed via a
Selector .
In order to be used with a selector, an instance of this class must
first be registered via the
SelectableChannel.register(Selector,int,Object)register method. This method returns a new
SelectionKey object
that represents the channel's registration with the selector.
Once registered with a selector, a channel remains registered until it
is deregistered. This involves deallocating whatever resources were
allocated to the channel by the selector.
A channel cannot be deregistered directly; instead, the key representing
its registration must be cancelled. Cancelling a key requests that
the channel be deregistered during the selector's next selection operation.
A key may be cancelled explicitly by invoking its
SelectionKey.cancel cancel method. All of a channel's keys are cancelled
implicitly when the channel is closed, whether by invoking its
Channel.close close method or by interrupting a thread blocked in an I/O
operation upon the channel.
If the selector itself is closed then the channel will be deregistered,
and the key representing its registration will be invalidated, without
further delay.
A channel may be registered at most once with any particular selector.
Whether or not a channel is registered with one or more selectors may be
determined by invoking the
SelectableChannel.isRegistered isRegistered method.
Selectable channels are safe for use by multiple concurrent
threads.
Blocking mode
A selectable channel is either in blocking mode or in
non-blocking mode. In blocking mode, every I/O operation invoked
upon the channel will block until it completes. In non-blocking mode an I/O
operation will never block and may transfer fewer bytes than were requested
or possibly no bytes at all. The blocking mode of a selectable channel may
be determined by invoking its
SelectableChannel.isBlocking isBlocking method.
Newly-created selectable channels are always in blocking mode.
Non-blocking mode is most useful in conjunction with selector-based
multiplexing. A channel must be placed into non-blocking mode before being
registered with a selector, and may not be returned to blocking mode until
it has been deregistered.
author:
Mark Reinhold
author:
JSR-51 Expert Group
version:
1.41, 07/05/05
since:
1.4
See Also: SelectionKey
See Also: Selector |
| Constructor Summary | |
| protected | SelectableChannel()
Initializes a new instance of this class. |
| Method Summary | |
| abstract public Object | blockingLock()
Retrieves the object upon which the
SelectableChannel.configureBlockingconfigureBlocking and
SelectableChannel.register register methods synchronize. | | abstract public SelectableChannel | configureBlocking(boolean block)
Adjusts this channel's blocking mode.
If this channel is registered with one or more selectors then an
attempt to place it into blocking mode will cause an
IllegalBlockingModeException to be thrown.
This method may be invoked at any time. | | abstract public boolean | isBlocking()
Tells whether or not every I/O operation on this channel will block
until it completes. | | abstract public boolean | isRegistered()
Tells whether or not this channel is currently registered with any
selectors. | | abstract public SelectionKey | keyFor(Selector sel)
Retrieves the key representing the channel's registration with the given
selector. | | abstract public SelectorProvider | provider()
Returns the provider that created this channel. | | abstract public SelectionKey | register(Selector sel, int ops, Object att)
Registers this channel with the given selector, returning a selection
key.
If this channel is currently registered with the given selector then
the selection key representing that registration is returned. | | final public SelectionKey | register(Selector sel, int ops)
Registers this channel with the given selector, returning a selection
key. | | abstract public int | validOps()
Returns an operation set
identifying this channel's supported operations. |
| SelectableChannel | | protected SelectableChannel()(Code) | | Initializes a new instance of this class.
|
| blockingLock | | abstract public Object blockingLock()(Code) | | Retrieves the object upon which the
SelectableChannel.configureBlockingconfigureBlocking and
SelectableChannel.register 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.
The blocking-mode lock object |
| configureBlocking | | abstract public SelectableChannel configureBlocking(boolean block) throws IOException(Code) | | Adjusts this channel's blocking mode.
If this channel is registered with one or more selectors then an
attempt to place it into blocking mode will cause an
IllegalBlockingModeException to be thrown.
This method may be invoked at any time. The new blocking mode will
only affect I/O operations that are initiated after this method returns.
For some implementations this may require blocking until all pending I/O
operations are complete.
If this method is invoked while another invocation of this method or
of the
SelectableChannel.register(Selector,int) register method is in progress
then it will first block until the other operation is complete.
Parameters:
block - If true then this channel will be placed inblocking mode; if false then it will be placednon-blocking mode This selectable channel
throws:
ClosedChannelException - If this channel is closed
throws:
IllegalBlockingModeException - If block is true and this channel isregistered with one or more selectors
throws:
IOException - If an I/O error occurs |
| isBlocking | | abstract public boolean isBlocking()(Code) | | 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.
true if, and only if, this channel is in blocking mode |
| isRegistered | | abstract public boolean isRegistered()(Code) | | 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.
true if, and only if, this channel is registered |
| keyFor | | abstract public SelectionKey keyFor(Selector sel)(Code) | | Retrieves the key representing the channel's registration with the given
selector.
The key returned when this channel was last registered with thegiven selector, or null if this channel is notcurrently registered with that selector |
| provider | | abstract public SelectorProvider provider()(Code) | | Returns the provider that created this channel.
The provider that created this channel |
| register | | abstract public SelectionKey register(Selector sel, int ops, Object att) throws ClosedChannelException(Code) | | Registers this channel with the given selector, returning a selection
key.
If this channel is currently registered with the given selector then
the selection key representing that registration is returned. The key's
interest set will have been changed to ops, as if by invoking
the
SelectionKey.interestOps(int) interestOps(int) method. If
the att argument is not null then the key's attachment
will have been set to that value. A
CancelledKeyException will
be thrown if the key has already been cancelled.
Otherwise this channel has not yet been registered with the given
selector, so it is registered and the resulting new key is returned.
The key's initial interest set will be ops and its attachment
will be att.
This method may be invoked at any time. If this method is invoked
while another invocation of this method or of the
SelectableChannel.configureBlocking(boolean) configureBlocking method is in progress
then it will first block until the other operation is complete. This
method will then synchronize on the selector's key set and therefore may
block if invoked concurrently with another registration or selection
operation involving the same selector.
If this channel is closed while this operation is in progress then
the key returned by this method will have been cancelled and will
therefore be invalid.
Parameters:
sel - The selector with which this channel is to be registered
Parameters:
ops - The interest set for the resulting key
Parameters:
att - The attachment for the resulting key; may be null
throws:
ClosedChannelException - If this channel is closed
throws:
IllegalBlockingModeException - If this channel is in blocking mode
throws:
IllegalSelectorException - If this channel was not created by the same provideras the given selector
throws:
CancelledKeyException - If this channel is currently registered with the given selectorbut the corresponding key has already been cancelled
throws:
IllegalArgumentException - If a bit in the ops set does not correspond to anoperation that is supported by this channel, that is, ifset & ~validOps() != 0 A key representing the registration of this channel withthe given selector |
| register | | final public SelectionKey register(Selector sel, int ops) throws ClosedChannelException(Code) | | Registers this channel with the given selector, returning a selection
key.
An invocation of this convenience method of the form
sc.register(sel, ops)
behaves in exactly the same way as the invocation
sc.
SelectableChannel.register(java.nio.channels.Selector,int,java.lang.Object)register (sel, ops, null)
Parameters:
sel - The selector with which this channel is to be registered
Parameters:
ops - The interest set for the resulting key
throws:
ClosedChannelException - If this channel is closed
throws:
IllegalBlockingModeException - If this channel is in blocking mode
throws:
IllegalSelectorException - If this channel was not created by the same provideras the given selector
throws:
CancelledKeyException - If this channel is currently registered with the given selectorbut the corresponding key has already been cancelled
throws:
IllegalArgumentException - If a bit in ops does not correspond to an operationthat is supported by this channel, that is, if set &~validOps() != 0 A key representing the registration of this channel withthe given selector |
| validOps | | abstract public int validOps()(Code) | | Returns an operation set
identifying this channel's supported operations. The bits that are set
in this integer value denote exactly the operations that are valid for
this channel. This method always returns the same value for a given
concrete channel class.
The valid-operation set |
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