ReusableUDPSelectorHandler.java

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package com.sun.grizzly;

import java.nio.channels.SelectableChannel;
import java.io.IOException;
import java.net.SocketAddress;
import java.net.InetSocketAddress;

/**
 * This class extends a UDP implementation of a <code>SelectorHandler</code>
 * and reuses the opened <code>DatagramChannel</code> if a user tries to connect any remote addresses.
 *
 * This class is useful for only CLIENT_SERVER Role.
 * Because of reusing the <code>DatagramChannel</code>,
 * if a user has initialized the <code>Selectorhandler</code> with <code>inet</code>,
 * when a user tries to connect a remote with a local address for binding it,
 * duplicated binding will be prevented.
 *
 * Here is scenario.
 * - opened a <code>DatagramChannel</code> from SelectorHandler with CLIENT_SERVER role
 * - tries to connect the remoteAddress with <code>Controller</code> like this.
 * "connectorHandler = controller.acquireConnectorHandler( Protocol.UDP );"
 * "connectorHandler.connect( remoteAddress, localAddress );"
 * Then, the opened <code>DatagramChannel</code> is reused for I/O operations.
 * Note: Actually, connectorHandler.close() doesn't allow the <code>DatagramChannel</code> to be closed
 * because the <code>DatagramChannel</code> is shared between server-side and client-side.
 * But you should guarantee calling connectorHandler.close() in order to prevent any connection leak,
 * after you have used connectorHandler.connect() once. 
 *
 * @author Bongjae Chang
 */
public class ReusableUDPSelectorHandler extends UDPSelectorHandler {

    public ReusableUDPSelectorHandler() {
        super( Role.CLIENT_SERVER );
    }

    @Override
    protected SelectableChannel getSelectableChannel( SocketAddress remoteAddress, SocketAddress localAddress ) throws IOException {
        SelectableChannel selectableChannel = null;
        if( localAddress != null ) {
            if( inet != null && localAddress instanceof InetSocketAddress ) {
                InetSocketAddress inetSocketAddress = (InetSocketAddress)localAddress;
                if( inet.equals( inetSocketAddress.getAddress() ) )
                    selectableChannel = getUsedSelectableChannel();
            }
        } else {
            selectableChannel = getUsedSelectableChannel();
        }
        if( selectableChannel == null )
            selectableChannel = super.getSelectableChannel( remoteAddress, localAddress );
        return selectableChannel;
    }

    private SelectableChannel getUsedSelectableChannel() {
        if( role != Role.CLIENT && datagramChannel != null && datagramSocket != null )
            return datagramChannel;
        else
            return null;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void closeChannel( SelectableChannel channel ) {
        if( datagramChannel == channel )
            return;
        super.closeChannel( channel );
    }
}