Class AbstractInterruptibleChannel

java.lang.Object

java.nio.channels.spi.AbstractInterruptibleChannel

All Implemented Interfaces:

Closeable, AutoCloseable, Channel, InterruptibleChannel

Direct Known Subclasses:

FileChannel, SelectableChannel

public abstract class AbstractInterruptibleChannel
extends Object
implements Channel, InterruptibleChannel

Base implementation class for interruptible channels.

This class encapsulates the low-level machinery required to implement the asynchronous closing and interruption of channels. A concrete channel 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:

    boolean completed = false;
    try {
        begin();
        completed = ...;    // Perform blocking I/O operation
        return ...;         // Return result
    } finally {
        end(completed);
    }

The completed argument to the end method tells whether or not the I/O operation actually completed, that is, whether it had any effect that would be visible to the invoker. In the case of an operation that reads bytes, for example, this argument should be true if, and only if, some bytes were actually transferred into the invoker's target buffer.

A concrete channel class must also implement the implCloseChannel method in such a way that if it is invoked while another thread is blocked in a native I/O operation upon the channel then that operation will immediately return, either by throwing an exception or by returning normally. If a thread is interrupted or the channel upon which it is blocked is asynchronously closed then the channel's end method will throw the appropriate exception.

This class performs the synchronization required to implement the Channel specification. Implementations of the implCloseChannel method need not synchronize against other threads that might be attempting to close the channel.

Since:

1.4

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	AbstractInterruptibleChannel()	Initializes a new instance of this class.

Method Summary

Modifier and Type	Method	Description
protected final void	begin()	Marks the beginning of an I/O operation that might block indefinitely.
final void	close()	Closes this channel.
protected final void	end(boolean completed)	Marks the end of an I/O operation that might block indefinitely.
protected abstract void	implCloseChannel()	Closes this channel.
final boolean	isOpen()	Tells whether or not this channel is open.

Methods declared in class Object

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

Modifier and Type	Method	Description
protected Object	clone()	Answers a new instance of the same class as the receiver, whose slots have been filled in with the values in the slots of the receiver.
boolean	equals(Object o)	Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison.
protected void	finalize()	Deprecated, for removal: This API element is subject to removal in a future version. May cause performance issues, deadlocks and hangs.
final Class<? extends Object>	getClass()	Answers the unique instance of java.lang.Class which represents the class of the receiver.
int	hashCode()	Answers an integer hash code for the receiver.
final void	notify()	Causes one thread which is waiting on the receiver to be made ready to run.
final void	notifyAll()	Causes all threads which are waiting on the receiver to be made ready to run.
String	toString()	Answers a string containing a concise, human-readable description of the receiver.
final void	wait()	Causes the thread which sent this message to be made not ready to run pending some change in the receiver (as indicated by notify or notifyAll).
final void	wait(long time)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.
final void	wait(long time, int frac)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.

Constructor Details

AbstractInterruptibleChannel

protected AbstractInterruptibleChannel()

Initializes a new instance of this class.

Method Details

close

public final void close()
                 throws IOException

Closes this channel.

If the channel has already been closed then this method returns immediately. Otherwise it marks the channel as closed and then invokes the implCloseChannel method in order to complete the close operation.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Channel

Specified by:

close in interface Closeable

Specified by:

close in interface InterruptibleChannel

Throws:

IOException - If an I/O error occurs

implCloseChannel

protected abstract void implCloseChannel()
                                  throws IOException

Closes this channel.

This method is invoked by the close method in order to perform the actual work of closing the channel. This method is only invoked if the channel 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 an I/O operation upon this channel to return immediately, either by throwing an exception or by returning normally.

Throws:

IOException - If an I/O error occurs while closing the channel

isOpen

public final boolean isOpen()

Description copied from interface: Channel

Tells whether or not this channel is open.

Specified by:

isOpen in interface Channel

Returns:

true if, and only if, this channel is open

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 asynchronous closing and interruption for this channel.

end

protected final void end(boolean completed)
                  throws AsynchronousCloseException

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 asynchronous closing and interruption for this channel.

Parameters:

completed - true if, and only if, the I/O operation completed successfully, that is, had some effect that would be visible to the operation's invoker

Throws:

AsynchronousCloseException - If the channel was asynchronously closed

ClosedByInterruptException - If the thread blocked in the I/O operation was interrupted