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import java.io.BufferedOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
/**
* Handle an Asynchronous OutputStream that allow to differ the writing process.
* This is an example purpose, and with this implementations IOException are uncaughted..
* Maybe we should use an UncaughtExceptionHandler to complete this design.
*
* All write() methods are ASynchronous but the close() method wait until all are "writted" to the destination outputstream
*
* Exemple to use:
*
* BufferedOutputStream bos = new BufferedOutputStream( new ASyncOutputStream( new FileOutputStream( "c:\\Test.txt" ) ) );
* bos.write( "A first line".getBytes() );
* bos.write( "A second one".getBytes() );
* bos.write( "the last one".getBytes() );
* bose.close();
*
* @author André Sébastien
*/
public class ASyncOutputStream extends OutputStream
{
private OutputStream out = null;
private ExecutorService es = null;
/** Creates a new instance of AsyncOutputStream */
public ASyncOutputStream(OutputStream o)
{
this.out = o;
this.es = Executors.newSingleThreadExecutor();
}
/**
* Writes the specified byte to this output stream. The general
* contract for <code>write</code> is that one byte is written
* to the output stream. The byte to be written is the eight
* low-order bits of the argument <code>b</code>. The 24
* high-order bits of <code>b</code> are ignored.
* <p>
* Subclasses of <code>OutputStream</code> must provide an
* implementation for this method.
*
*
* @param b the <code>byte</code>.
* @exception IOException if an I/O error occurs. In particular,
* an <code>IOException</code> may be thrown if the
* output stream has been closed.
*/
public void write(final int b) throws IOException {
Runnable doRun = new Runnable()
{
public void run()
{
try
{
ASyncOutputStream.this.out.write(b);
}
catch(Exception e)
{ /* Maybe you should handle theses exceptions by a UncaughtExceptionHandler */
e.printStackTrace();
}
}
};
this.es.execute(doRun);
}
/**
* Writes <code>len</code> bytes from the specified byte array
* starting at offset <code>off</code> to this output stream.
* The general contract for <code>write(b, off, len)</code> is that
* some of the bytes in the array <code>b</code> are written to the
* output stream in order; element <code>b[off]</code> is the first
* byte written and <code>b[off+len-1]</code> is the last byte written
* by this operation.
* <p>
* The <code>write</code> method of <code>OutputStream</code> calls
* the write method of one argument on each of the bytes to be
* written out. Subclasses are encouraged to override this method and
* provide a more efficient implementation.
* <p>
* If <code>b</code> is <code>null</code>, a
* <code>NullPointerException</code> is thrown.
* <p>
* If <code>off</code> is negative, or <code>len</code> is negative, or
* <code>off+len</code> is greater than the length of the array
* <code>b</code>, then an <tt>IndexOutOfBoundsException</tt> is thrown.
*
*
* @param b the data.
* @param off the start offset in the data.
* @param len the number of bytes to write.
* @exception IOException if an I/O error occurs. In particular,
* an <code>IOException</code> is thrown if the output
* stream is closed.
*/
public void write(final byte[] b, final int off, final int len) throws IOException {
Runnable doRun = new Runnable()
{
public void run()
{
try
{
ASyncOutputStream.this.out.write(b,off,len);
}
catch(Exception e)
{ /* Maybe you should handle theses exceptions by a UncaughtExceptionHandler */
e.printStackTrace();
}
}
};
this.es.execute(doRun);
}
/**
* Closes this output stream and releases any system resources
* associated with this stream. The general contract of <code>close</code>
* is that it closes the output stream. A closed stream cannot perform
* output operations and cannot be reopened.
* <p>
* The <code>close</code> method of <code>OutputStream</code> does nothing.
*
*
* @exception IOException if an I/O error occurs.
*/
public void close() throws IOException {
super.close();
Runnable doRun = new Runnable()
{
public void run()
{
try
{
ASyncOutputStream.this.out.close();
ASyncOutputStream.this.es.shutdown();
}
catch(Exception e)
{ /* Maybe you should handle theses exceptions by a UncaughtExceptionHandler */
e.printStackTrace();
}
}
};
// Execute and wait the sucess
Future future = this.es.submit(doRun);
try
{
future.get();
}
catch(Exception e){ e.printStackTrace(); }
}
/**
* Flushes this output stream and forces any buffered output bytes
* to be written out. The general contract of <code>flush</code> is
* that calling it is an indication that, if any bytes previously
* written have been buffered by the implementation of the output
* stream, such bytes should immediately be written to their
* intended destination.
* <p>
* If the intended destination of this stream is an abstraction provided by
* the underlying operating system, for example a file, then flushing the
* stream guarantees only that bytes previously written to the stream are
* passed to the operating system for writing; it does not guarantee that
* they are actually written to a physical device such as a disk drive.
* <p>
* The <code>flush</code> method of <code>OutputStream</code> does nothing.
*
*
* @exception IOException if an I/O error occurs.
*/
public void flush() throws IOException {
super.flush();
Runnable doRun = new Runnable()
{
public void run()
{
try
{
ASyncOutputStream.this.out.flush();
}
catch(Exception e)
{ /* Maybe you should handle theses exceptions by a UncaughtExceptionHandler */
e.printStackTrace();
}
}
};
this.es.execute(doRun);
}
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
try
{
BufferedOutputStream bos = new BufferedOutputStream( new ASyncOutputStream( new FileOutputStream( "c:\\Test.txt" ) ) );
bos.write( "A first line".getBytes() );
bos.write( "A second one".getBytes() );
bos.write( "the last one".getBytes() );
bos.close();
}
catch(Exception e){ e.printStackTrace(); }
}
} |
[Thread] écriture d'un fichier de façon asynchrone
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