- java.lang.Object
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- java.nio.channels.spi.AbstractInterruptibleChannel
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- 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
andend
methods before and after, respectively, invoking an I/O operation that might block indefinitely. In order to ensure that theend
method is always invoked, these methods should be used within atry
...finally
block:boolean completed = false; try { begin(); completed = ...; // Perform blocking I/O operation return ...; // Return result } finally { end(completed); }
The
completed
argument to theend
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 betrue
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'send
method will throw the appropriate exception.This class performs the synchronization required to implement the
Channel
specification. Implementations of theimplCloseChannel
method need not synchronize against other threads that might be attempting to close the channel.- Since:
- 1.4
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Constructor Summary
Constructors Modifier Constructor Description protected
AbstractInterruptibleChannel()
Initializes a new instance of this class.
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description protected void
begin()
Marks the beginning of an I/O operation that might block indefinitely.void
close()
Closes this channel.protected void
end(boolean completed)
Marks the end of an I/O operation that might block indefinitely.protected abstract void
implCloseChannel()
Closes this channel.
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Method Detail
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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 interfaceAutoCloseable
- Specified by:
close
in interfaceChannel
- Specified by:
close
in interfaceCloseable
- Specified by:
close
in interfaceInterruptibleChannel
- Throws:
IOException
- If an I/O error occurs
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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
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begin
protected final void begin()
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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 atry
...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 closedClosedByInterruptException
- If the thread blocked in the I/O operation was interrupted
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