java.lang.Object
java.nio.channels.Selector
- Direct Known Subclasses:
- AbstractSelector
- See Also:
- Top Examples, Source Code,
ConcurrentModificationException, iterator, interrupt, wakeup, selectNow(), select(long), select(), remove, remove, cancel, register, selectedKeys, keys, close, openSelector, open
public abstract void close()
throws IOException- See Also:
-
ClosedSelectorException, wakeup
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
[240]Non-blocking I/O
By Anonymous on 2004/12/17 01:04:51 Rate
// non-blocking I/O:
import java.nio.channels.*;
import java.util.*;
// Create a selector object to monitor all open client connections.
Selector selector = Selector.open ( ) ;
// Create a new non-blocking ServerSocketChannel, bind it to port 8000, and
// register it with the Selector
ServerSocketChannel server = ServerSocketChannel.open ( ) ; // Open channel
server.configureBlocking ( false ) ; // Non-blocking
server.socket ( ) .bind ( new java.net.InetSocketAddress ( 8000 ) ) ; // Bind to port
SelectionKey serverkey = server.register ( selector, SelectionKey.OP_ACCEPT ) ;
for ( ;; ) { // The main server loop. The server runs forever.
// This call blocks until there is activity on one of the
// registered channels. This is the key method in non-blocking I/O.
selector.select ( ) ;
// Get a java.util.Set containing the SelectionKey objects for
// all channels that are ready for I/O.
Set keys = selector.selectedKeys ( ) ;
// Use a java.util.Iterator to loop through the selected keys
for ( Iterator i = keys.iterator ( ) ; i.hasNext ( ) ; ) {
SelectionKey key = ( SelectionKey ) i.next ( ) ;
i.remove ( ) ; // Remove the key from the set of selected keys
// Check whether this key is the SelectionKey we got when
// we registered the ServerSocketChannel.
if ( key == serverkey ) {
// Activity on the ServerSocketChannel means a client
// is trying to connect to the server.
if ( key.isAcceptable ( ) ) {
// Accept the client connection
SocketChannel client = server.accept ( ) ;
// Put the client channel in non-blocking mode.
client.configureBlocking ( false ) ;
// Now register the client channel with the Selector object
SelectionKey clientkey =
client.register ( selector, SelectionKey.OP_READ ) ;
}
}
else { // Otherwise, there must be activity on a client channel
// Double-check that there is data to read
if ( !key.isReadable ( ) ) continue;
// Get the client channel that has data to read
SocketChannel client = ( SocketChannel ) key.channel ( ) ;
// Now read bytes from the client into a buffer allocated elsewhere
int bytesread = client.read ( buffer ) ;
// If read ( ) returns -1, it indicates end-of-stream, which
// means the client has disconnected, so de-register the
// selection key and close the channel.
if ( bytesread == -1 ) {
key.cancel ( ) ;
client.close ( ) ;
continue;
}
}
}
}
public abstract boolean isOpen()
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public abstract Set<SelectionKey> keys()
- See Also:
- ClosedSelectorException,
UnsupportedOperationException
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public static Selector open()
throws IOException- See Also:
-
SelectorProvider, openSelector
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public abstract SelectorProvider provider()
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public abstract int select()
throws IOException- See Also:
- ClosedSelectorException,
wakeup
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
[1764]The Selector on which the SocketChannel has been registered is exhausted,
By Anonymous on 2006/05/31 11:10:09 Rate
while ( bb.hasRemaining ( ) ) {
// *** socketChannel will always return 0
int len = socketChannel.write ( bb ) ;
if ( len < 0 ) {
throw new EOFException ( ) ;
}
}
This code will works most of the time....until the Selector on which the SocketChannel has been registered is exhausted, e.g the Selector isn't able to let the socketChannel flush the content of the ByteBuffer. , which means: he CPU will be consumed by looping over and over, producing disastrous performance problem
public abstract int select(long timeout)
throws IOException- See Also:
- IllegalArgumentException, ClosedSelectorException,
Object.wait(long), wakeup
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public abstract Set<SelectionKey> selectedKeys()
- See Also:
- ClosedSelectorException,
UnsupportedOperationException
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public abstract int selectNow()
throws IOException- See Also:
- ClosedSelectorException,
wakeup
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
protected Selector()
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
[1765]Use a temporary Selector
By Anonymous on 2006/05/31 11:14:51 Rate
If the main Selector is exhausted, a temporary Selector will be used to handle the OP_WRITE.
try {
while ( bb.hasRemaining ( ) ) {
int len = socketChannel.write ( bb ) ;
attempts++;
if ( len < 0 ) {
throw new EOFException ( ) ;
}
if ( len == 0 ) {
if ( writeSelector == null ) {
writeSelector = SelectorFactory.getSelector ( ) ;
if ( writeSelector == null ) {
// Continue using the main one.
continue;
}
}
key = socketChannel.register ( writeSelector, key.OP_WRITE ) ;
if ( writeSelector.select ( 30 * 1000 ) == 0 ) {
if ( attempts > 2 )
throw new IOException ( "Client disconnected" ) ;
} else {
attempts--;
}
} else {
attempts = 0;
}
}
} finally {
if ( key != null ) {
key.cancel ( ) ;
key = null;
}
if ( writeSelector != null ) {
// Flush the key.
writeSelector.selectNow ( ) ;
SelectorFactory.returnSelector ( writeSelector ) ;
}
}
public abstract Selector wakeup()
- See Also:
select(long), select(), selectNow()
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
Java API By Example, From Geeks To Geeks.