Java in a Nutshell, 5th Edition [Electronic resources] نسخه متنی

This abstract class defines the API for
channels that can be used with a Selector object
to allow a thread to block while waiting for activity on any of a
group of channels. All channel classes in the
java.nio.channels package except for
FileChannel are subclasses of
SelectableChannel.

A selectable channel may only be registered with a
Selector if it is nonblocking, so this class
defines the configureBlocking(
)
method. Pass false to this method to put a channel
into nonblocking mode, or pass TRue to make calls
to its read( ) and/or write( )
methods block. Use isBlocking( ) to determine the
current blocking mode of a selectable channel.

Register a SelectableChannel with a
Selector by calling the register(
) method of the channel (not
of the selector). There are two versions of this method: both take a
Selector object and a bitmask that specifies the
set of channel operations that are to be
"selected" on that channel. (see
SelectionKey for the constants that can be OR-ed
together to form this bitmask). Both methods return a
SelectionKey object that represents the
registration of the channel with the selector. One version of the
register( ) method also takes an arbitrary object
argument which serves as an
"attachment" to the
SelectionKey and allows you to associate arbitrary
data with it. The validOps( ) method returns a
bitmask that specifies the set of operations that a particular
channel object allows to be selected. The bitmask
passed to register( ) may only contain bits that
are set in this validOps( ) value.

Note that SelectableChannel does not define a
deregister( ) method. Instead, to remove a channel
from the set of channels being monitored by a
Selector, you must call the cancel(
) method of the SelectionKey returned by
register( ).

Call isRegistered(
) to determine whether a
SelectableChannel is registered with any
Selector. (Note that a single channel may be
registered with more than one Selector.) If you
did not keep track of the SelectionKey returned by
a call to register( ), you can query it with the
keyFor( ) method.

See Selector and SelectionKey
for further details on multiplexing selectable channels.

Figure 13-37. java.nio.channels.SelectableChannel

public abstract class

SelectableChannel extends java.nio.channels.spi.
AbstractInterruptibleChannel implements Channel {
// Protected Constructors
protected

SelectableChannel ( );
// Public Instance Methods
public abstract Object

blockingLock ( );
public abstract SelectableChannel

configureBlocking (boolean

block )
throws java.io.IOException;
public abstract boolean

isBlocking ( );
public abstract boolean

isRegistered ( );
public abstract SelectionKey

keyFor (Selector

sel );
public abstract java.nio.channels.spi.SelectorProvider

provider ( );
public final SelectionKey

register (Selector

sel , int

ops )
throws ClosedChannelException;
public abstract SelectionKey

register (Selector

sel , int

ops , Object

att )
throws ClosedChannelException;
public abstract int

validOps ( );
}

Subclasses

java.nio.channels.spi.AbstractSelectableChannel

Returned By

SelectionKey.channel( ),
java.nio.channels.spi.AbstractSelectableChannel.configureBlocking(
)