Base implementation class for selectors.
This class encapsulates the low-level machinery required to implement
the interruption of selection operations. A concrete selector class must
invoke the begin
and end
methods before and
after, respectively, invoking an I/O operation that might block
indefinitely. In order to ensure that the end
method is always
invoked, these methods should be used within a
try ... finally block:
try { begin(); // Perform blocking I/O operation here ... } finally { end(); }
This class also defines methods for maintaining a selector's
cancelled-key set and for removing a key from its channel's key set, and
declares the abstract register
method that is invoked by a
selectable channel's register
method in order to perform the actual work of registering a channel.
Protected Constructor Summary
Public Method Summary
final void |
close()
Closes this selector.
|
final boolean |
isOpen()
Tells whether or not this selector is open.
|
final SelectorProvider |
provider()
Returns the provider that created this channel.
|
Protected Method Summary
final void |
begin()
Marks the beginning of an I/O operation that might block indefinitely.
|
final Set<SelectionKey> |
cancelledKeys()
Retrieves this selector's cancelled-key set.
|
final void | |
final void |
end()
Marks the end of an I/O operation that might block indefinitely.
|
abstract void |
implCloseSelector()
Closes this selector.
|
abstract SelectionKey |
register(AbstractSelectableChannel ch, int ops, Object att)
Registers the given channel with this selector.
|
Inherited Method Summary
Protected Constructors
protected AbstractSelector (SelectorProvider provider)
Initializes a new instance of this class.
Parameters
provider | The provider that created this selector |
---|
Public Methods
public final void close ()
Closes this selector.
If the selector has already been closed then this method returns
immediately. Otherwise it marks the selector as closed and then invokes
the implCloseSelector
method in order to
complete the close operation.
Throws
IOException | If an I/O error occurs |
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public final boolean isOpen ()
Tells whether or not this selector is open.
Returns
- true if, and only if, this selector is open
public final SelectorProvider provider ()
Returns the provider that created this channel.
Returns
- The provider that created this channel
Protected Methods
protected final void begin ()
Marks the beginning of an I/O operation that might block indefinitely.
This method should be invoked in tandem with the end
method, using a try ... finally block as
shown above, in order to implement interruption for
this selector.
Invoking this method arranges for the selector's wakeup
method to be invoked if a thread's interrupt
method is invoked while the thread is
blocked in an I/O operation upon the selector.
protected final Set<SelectionKey> cancelledKeys ()
Retrieves this selector's cancelled-key set.
This set should only be used while synchronized upon it.
Returns
- The cancelled-key set
protected final void deregister (AbstractSelectionKey key)
Removes the given key from its channel's key set.
This method must be invoked by the selector for each channel that it deregisters.
Parameters
key | The selection key to be removed |
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protected final void end ()
protected abstract void implCloseSelector ()
Closes this selector.
This method is invoked by the close
method in order
to perform the actual work of closing the selector. This method is only
invoked if the selector 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 a selection operation upon this selector to return
immediately as if by invoking the wakeup
method.
Throws
IOException | If an I/O error occurs while closing the selector |
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protected abstract SelectionKey register (AbstractSelectableChannel ch, int ops, Object att)
Registers the given channel with this selector.
This method is invoked by a channel's register
method in order to perform
the actual work of registering the channel with this selector.
Parameters
ch | The channel to be registered |
---|---|
ops | The initial interest set, which must be valid |
att | The initial attachment for the resulting key |
Returns
- A new key representing the registration of the given channel with this selector