java.nio.channels.spi.AbstractSelector

All Implemented Interfaces:: Closeable, AutoCloseable

public abstract class AbstractSelector
extends Selector

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.

Since:: 1.4

Constructor Summary

Constructors

Modifier Constructor Description

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

Method Summary

Modifier and Type	Method	Description
`protected void`	`begin()`	Marks the beginning of an I/O operation that might block indefinitely.
`protected Set<SelectionKey>`	`cancelledKeys()`	Retrieves this selector's cancelled-key set.
`void`	`close()`	Closes this selector.
`protected void`	`deregister(AbstractSelectionKey key)`	Removes the given key from its channel's key set.
`protected void`	`end()`	Marks the end of an I/O operation that might block indefinitely.
`protected abstract void`	`implCloseSelector()`	Closes this selector.
`SelectorProvider`	`provider()`	Returns the provider that created this channel.
`protected abstract SelectionKey`	`register(AbstractSelectableChannel ch, int ops, Object att)`	Registers the given channel with this selector.

Methods declared in class java.nio.channels.Selector

isOpen, keys, open, select, select, select, select, selectedKeys, selectNow, selectNow, wakeup

Methods declared in class java.lang.Object

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

Constructor Details
- AbstractSelector
  
  protected AbstractSelector(SelectorProvider provider)
  
  Initializes a new instance of this class.
  
  Parameters:
  
  provider - The provider that created this selector
Method Details
- close
  
  public final void close() throws IOException
  
  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.
  
  Specified by:
  
  close in interface AutoCloseable
  
  Specified by:
  
  close in interface Closeable
  
  Specified by:
  
  close in class Selector
  
  Throws:
  
  IOException - If an I/O error occurs
- implCloseSelector
  
  protected abstract void implCloseSelector() throws IOException
  
  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
- provider
  
  public final SelectorProvider provider()
  
  Returns the provider that created this channel.
  
  Specified by:
  
  provider in class Selector
  
  Returns:
  
  The provider that created this channel
- cancelledKeys
  
  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
- register
  
  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
- deregister
  
  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
- begin
  
  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.
- end
  
  protected final void end()
  
  Marks the end of an I/O operation that might block indefinitely.
  This method should be invoked in tandem with the begin method, using a try ... finally block as shown above, in order to implement interruption for this selector.

Class AbstractSelector

Constructor Summary

Method Summary

Methods declared in class java.nio.channels.Selector

Methods declared in class java.lang.Object

Constructor Details

Method Details