NIO2 API

org.classpath.icedtea.java.nio.channels
Interface AsynchronousChannel

All Superinterfaces:
Channel, Closeable
All Known Subinterfaces:
AsynchronousByteChannel
All Known Implementing Classes:
AsynchronousDatagramChannel, AsynchronousFileChannel, AsynchronousServerSocketChannel, AsynchronousSocketChannel

public interface AsynchronousChannel
extends Channel

A channel that supports asynchronous I/O operations. Asynchronous I/O operations will usually take one of two forms:

  1. Future<V> operation(...)
  2. Future<V> operation(... A attachment, CompletionHandler<V,? super A> handler)
where operation is the name of the I/O operation (read or write for example), V is the result type of the I/O operation, and A is the type of an object attached to the I/O operation to provide context when consuming the result. The attachment is important for cases where a state-less CompletionHandler is used to consume the result of many I/O operations.

In the first form, the methods defined by the Future interface may be used to check if the operation has completed, wait for its completion, and to retrieve the result. In the second form, a CompletionHandler is invoked to consume the result of the I/O operation when it completes, fails, or is cancelled.

A channel that implements this interface is asynchronously closeable: If an I/O operation is outstanding on the channel and the channel's close method is invoked, then the I/O operation fails with the exception AsynchronousCloseException.

Asynchronous channels are safe for use by multiple concurrent threads. Some channel implementations may support concurrent reading and writing, but may not allow more than one read and one write operation to be outstanding at any given time.

Cancellation

The Future interface defines the cancel method to cancel execution of a task.

Where the cancel method is invoked with the mayInterruptIfRunning parameter set to true then the I/O operation may be interrupted by closing the channel. This will cause any other I/O operations outstanding on the channel to complete with the exception AsynchronousCloseException.

If a CompletionHandler is specified when initiating an I/O operation, and the cancel method is invoked to cancel the I/O operation before it completes, then the CompletionHandler's cancelled method is invoked.

If an implementation of this interface supports a means to cancel I/O operations, and where cancellation may leave the channel, or the entity to which it is connected, in an inconsistent state, then the channel is put into an implementation specific error state that prevents further attempts to initiate I/O operations on the channel. For example, if a read operation is cancelled but the implementation cannot guarantee that bytes have not been read from the channel then it puts the channel into error state state; further attempts to initiate a read operation causes an unspecified runtime exception to be thrown.

Where the cancel method is invoked to cancel read or write operations then it recommended that all buffers used in the I/O operations be discarded or care taken to ensure that the buffers are not accessed while the channel remains open.

Since:
1.7

Method Summary
 void close()
          Closes this channel.
 
Methods inherited from interface java.nio.channels.Channel
isOpen
 

Method Detail

close

void close()
           throws IOException
Closes this channel.

Any outstanding asynchronous operations upon this channel will complete with the exception AsynchronousCloseException. After a channel is closed then further attempts to initiate asynchronous I/O operations complete immediately with cause ClosedChannelException.

This method otherwise behaves exactly as specified by the Channel interface.

Specified by:
close in interface Channel
Specified by:
close in interface Closeable
Throws:
IOException - If an I/O error occurs

NIO2 API

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