org.refcodes.connection.impls.AbstractReceiver Maven / Gradle / Ivy
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// /////////////////////////////////////////////////////////////////////////////
// REFCODES.ORG
// =============================================================================
// This code is copyright (c) by Siegfried Steiner, Munich, Germany and licensed
// under the following (see "http://en.wikipedia.org/wiki/Multi-licensing")
// licenses:
// =============================================================================
// GNU General Public License, v3.0 ("http://www.gnu.org/licenses/gpl-3.0.html")
// together with the GPL linking exception applied; as being applied by the GNU
// Classpath ("http://www.gnu.org/software/classpath/license.html")
// =============================================================================
// Apache License, v2.0 ("http://www.apache.org/licenses/LICENSE-2.0")
// =============================================================================
// Please contact the copyright holding author(s) of the software artifacts in
// question for licensing issues not being covered by the above listed licenses,
// also regarding commercial licensing models or regarding the compatibility
// with other open source licenses.
// /////////////////////////////////////////////////////////////////////////////
package org.refcodes.connection.impls;
import java.io.Serializable;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.TimeUnit;
import org.refcodes.component.impls.AbstractConnectableAutomaton;
import org.refcodes.component.traps.OpenException;
import org.refcodes.connection.Receiver;
import org.refcodes.controlflow.RetryCounter;
import org.refcodes.controlflow.impls.RetryCounterImpl;
import org.refcodes.data.consts.ControlFlowConsts;
import org.refcodes.logger.RuntimeLogger;
import org.refcodes.logger.factories.impls.RuntimeLoggerFactorySingleton;
/**
* The {@link AbstractReceiver} is a base abstract implementation of the
* {@link Receiver} interface providing common functionality for concrete real
* live {@link Receiver} implementations.
*
* A blocking queue is used internally to which received datagrams are put via
* {@link #pushDatagram(Serializable)} and which can be retrieved via
* {@link #readDatagram()}.
*
* Make sure your code fetches the datagrams quick enough to prevent filling up
* of the queue. In case the queue is filled up, adding elements via
* {@link #pushDatagram(Serializable)} to the queue is blocked until elements
* are taken from the queue via {@link #readDatagram()}.
*
* @param The type of the datagram to be operated with.
*/
public abstract class AbstractReceiver extends AbstractConnectableAutomaton implements Receiver {
private static RuntimeLogger LOGGER = RuntimeLoggerFactorySingleton.getInstance().createInstance();
// /////////////////////////////////////////////////////////////////////////
// CONSTANTS:
// /////////////////////////////////////////////////////////////////////////
private static final int MAX_MESSAGE_QUEUE_SIZE = 1000;
// /////////////////////////////////////////////////////////////////////////
// VARIABLES:
// /////////////////////////////////////////////////////////////////////////
private LinkedBlockingQueue _datagramQueue;
// /////////////////////////////////////////////////////////////////////////
// CONSTRUCTORS:
// /////////////////////////////////////////////////////////////////////////
/**
* Constructs a {@link AbstractReceiver} with a default sized blocking queue
* enabling a maximum of {@link #MAX_MESSAGE_QUEUE_SIZE} datagrams.
* -------------------------------------------------------------------------
* Make sure your code fetches the datagrams quick enough to prevent filling
* up of the queue. In case the queue is filled up, adding elements via
* {@link #pushDatagram(Serializable)} to the queue is blocked until
* elements are taken from the queue via {@link #readDatagram()}.
*/
public AbstractReceiver() {
_datagramQueue = new LinkedBlockingQueue( MAX_MESSAGE_QUEUE_SIZE );
}
/**
* Constructs a {@link AbstractReceiver} with a custom sized blocking queue
* enabling a maximum of datagrams as specified by the capacity parameter.
* -------------------------------------------------------------------------
* Make sure your code fetches the datagrams quick enough to prevent filling
* up of the queue. In case the queue is filled up, adding elements via
* {@link #pushDatagram(Serializable)} to the queue is blocked until
* elements are taken from the queue via {@link #readDatagram()}.
*
* @param aCapacity The capacity of the queue holding the received
* datagrams.
*/
public AbstractReceiver( int aCapacity ) {
_datagramQueue = new LinkedBlockingQueue( aCapacity );
}
// /////////////////////////////////////////////////////////////////////////
// METHODS:
// /////////////////////////////////////////////////////////////////////////
/**
* {@inheritDoc}
*/
@Override
public DATA readDatagram() throws OpenException, InterruptedException {
// Enable the caller to get all elements from the queue:
if ( _datagramQueue.isEmpty() && !isOpened() ) {
throw new OpenException( "Unable to read datagram as the connection is NOT OPEN; connection status is " + getConnectionStatus() + "." );
}
return _datagramQueue.take();
}
/**
* {@inheritDoc}
*/
@Override
public boolean hasDatagram() throws OpenException {
// Enable the caller to get all elements from the queue:
if ( _datagramQueue.isEmpty() && !isOpened() ) {
throw new OpenException( "Unable to read datagram as the connection is NOT OPEN; connection status is " + getConnectionStatus() + "." );
}
return !_datagramQueue.isEmpty();
}
/**
* {@inheritDoc}
*/
@Override
public void close() {
if ( isOpened() ) {
super.close();
releaseAll();
}
}
/**
* {@inheritDoc}
*/
@Override
public void releaseAll() {
synchronized ( _datagramQueue ) {
_datagramQueue.notifyAll();
}
}
// /////////////////////////////////////////////////////////////////////////
// HOOKS:
// /////////////////////////////////////////////////////////////////////////
/**
* Pushes a datagram into the receiver and puts it into the blocking queue
* containing the so far received datagrams. Them datagrams can be retrieved
* via {@link #readDatagram()}: use {@link #hasDatagram()} to test
* beforehand whether there is a datagram available.
*
* @param aDatagram The datagram to be pushed at the end of the blocking
* queue; to be retrieved with the {@link #readDatagram()} method.
*/
protected void pushDatagram( DATA aDatagram ) throws OpenException {
if ( !isOpened() ) {
throw new OpenException( "Unable to push datagram <" + aDatagram.getClass().getName() + "> as the connection is NOT OPEN; connection status is " + getConnectionStatus() + "." );
}
RetryCounter theRetryCounter = new RetryCounterImpl( ControlFlowConsts.MAX_IO_RETRIES );
try {
while ( !_datagramQueue.offer( aDatagram, ControlFlowConsts.MAX_CODE_LOOP_SLEEP_TIME_IN_MS, TimeUnit.MILLISECONDS ) && theRetryCounter.nextRetry() ) {
LOGGER.warn( "Trying to offer (add) a datagram to the datagram queue, though the queue is full, this is retry # <" + theRetryCounter.getRetryCount() + ">, aborting after <" + theRetryCounter.getRetryNumber() + "> retries. Retrying now after a delay of <" + (ControlFlowConsts.MAX_CODE_LOOP_SLEEP_TIME_IN_MS / 1000) + "> seconds..." );
if ( !theRetryCounter.hasNextRetry() ) {
throw new OpenException( "Unable to process the datagram after <" + theRetryCounter.getRetryNumber() + "> retries, aborting retries, dismissing datagram \"" + aDatagram.toString() + "\"!", null, null );
}
}
}
catch ( InterruptedException e ) { /* ignore */}
}
}