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| Code Block | ||
|---|---|---|
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@Override
public void processInOpen() throws IOException {
if (!preload) {
final File file = new File(filename);
try {
in = new FileInputStream(file);
fireOnConnect();
} catch (Exception e) {
fireOnDisconnect();
throw e;
}
} else {
fis = new FileInputStream(filename);
FileChannel channel = fis.getChannel();
long size = channel.size();
double x = size / (double) Integer.MAX_VALUE;
int n = (int) Math.ceil(x);
ByteBuffer buffers[] = new ByteBuffer[n];
for (int i = 0; i < n; i++) {
buffers[i] = ByteBuffer.allocateDirect(Integer.MAX_VALUE);
channel.read(buffers[i]);
buffers[i].rewind();
}
in = createInputStream(buffers);
fireOnConnect();
}
}
@Override
public void processInClose() throws IOException {
super.processInClose();
if (fis != null) {
fis.close();
}
}
@Override
public void processOutOpen() throws IOException {
final File file = new File(filename);
try {
out = new FileOutputStream(file, append);
fireOnConnect();
} catch (Exception e) {
fireOnDisconnect();
throw e;
}
}
@Override
public void processOutClose() throws IOException {
fireOnDisconnect();
out.flush();
out.close();
} |
Imporant: Use processInStart if the transport handler connects to a service that immediatly sends data!
Hint: There are scenarios in which it is not feasible to separate transport and protocol layer. In such cases, one can implement the combination as a transport handler and use it in combination with the "None" protocol handler.
Generic Pull
After the connection is inialized, the framework tries to retrieve data from the TransportHandler. To be generic, we decided to use an InputStream for sources and an OutputStream for sinks. So the following methods need to be overwritten (Remark: It its not necessary to implement both methods, if the TransportHandler e.g. should only be used for sources):
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Another way, implementing a transport handler that is less generic and delivers e.g. tuples directly can be found in the next example. In this case, the protocol handler must be 'none' ..
| Code Block | ||
|---|---|---|
| ||
package de.uniol.inf.is.odysseus.wrapper.temper1.physicaloperator.access;
import java.util.Map;
import java.util.Random;
import de.uniol.inf.is.odysseus.core.collection.Tuple;
import de.uniol.inf.is.odysseus.core.physicaloperator.access.protocol.IProtocolHandler;
import de.uniol.inf.is.odysseus.core.physicaloperator.access.transport.AbstractSimplePullTransportHandler;
import de.uniol.inf.is.odysseus.core.physicaloperator.access.transport.ITransportHandler;
public class RandomTransportHandler extends AbstractSimplePullTransportHandler<Tuple<?>>{
private static final String NAME = "Random";
private static final Random RAND = new Random();
@Override
public ITransportHandler createInstance(IProtocolHandler<?> protocolHandler, Map<String, String> options) {
RandomTransportHandler tHandler = new RandomTransportHandler();
protocolHandler.setTransportHandler(tHandler);
return tHandler;
}
@Override
public String getName() {
return NAME;
}
private static float readDevice() {
return 20f + ( 10 * RAND.nextFloat());
}
@Override
public boolean hasNext() {
return true;
}
@SuppressWarnings("rawtypes")
@Override
public Tuple<?> getNext() {
Tuple<?> tuple = new Tuple(1, false);
tuple.setAttribute(0, readDevice());
return tuple;
}
@Override
public boolean isSemanticallyEqualImpl(ITransportHandler other) {
return false;
}
}
|
...
GenericPush
In generic push szenarios for sources there is no method that can be overwritten because it depends on the transport type and e.g. libararies that receive data from external sources. The information that is read must be send to the corresponding transport handler. To simplify the process, AbstractTransportHandler(Delegate) provides the following methods that should be used:
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The fireProcess methods can be used with ByteBuffers and String-Arrays or with a Generic. In the latter case, the corresponding ProtocolHandler must read this type, else a class cast exception will be thrown.
Important: A transport handler must not send data before processInStart is called!
An example to An example to the use fireProcess-Methods (and processInOpen/processInStart) can be found in the RabbitMQ transport handler:
| Code Block | ||
|---|---|---|
| ||
@Override public void processInOpen() throws IOException { internalOpen();try { // Create ConsumerinternalOpen(); } booleancatch autoAck(TimeoutException =e1) false;{ channel.basicConsume(queueName, autoAck, consumerTag, // TODO Auto-generated catch block new DefaultConsumer(channel e1.printStackTrace(); } } @Override public void processInStart() { try { @Override if (publishStyle == PublishStyle.PublishSubscribe) { String queueName = channel.queueDeclare().getQueue(); channel.queueBind(queueName, exchangeName, ""); } // Create Consumer boolean autoAck = false; channel.basicConsume(queueName, autoAck, consumerTag, new DefaultConsumer(channel) { @Override public void handleDelivery(String consumerTag, com.rabbitmq.client.Envelope envelope, com.rabbitmq.client.AMQP.BasicProperties properties, byte[] body) throws IOException { // String routingKey = envelope.getRoutingKey(); // String contentType = properties.getContentType(); long deliveryTag = envelope.getDeliveryTag(); public void handleDelivery( try { String consumerTag, ByteBuffer wrapped = ByteBuffer.wrap(body); comwrapped.rabbitmq.client.Envelope envelope, position(wrapped.limit()); fireProcess(wrapped); com.rabbitmq.client.AMQP.BasicProperties properties, } catch (Exception e) { byte[] body) throws IOException { // LOG.warn("Error processing input", e); String routingKey = envelope.getRoutingKey(); // } String contentType = propertieschannel.getContentTypebasicAck(deliveryTag, false); }; long deliveryTag = envelope.getDeliveryTag(}); connection.addShutdownListener(new ShutdownListener() try{ @Override ByteBuffer wrapped = ByteBuffer.wrap(body); public void shutdownCompleted(ShutdownSignalException cause) { wrappedLOG.position(wrapped.limit())warn("Connection shutdown.", cause); } fireProcess(wrapped}); channel.addShutdownListener(new ShutdownListener() { }catch(Exception e){ @Override public void e.printStackTrace();shutdownCompleted(ShutdownSignalException cause) { LOG.warn("Channel shutdown.", cause); } } channel.basicAck(deliveryTag, false }); } catch (IOException e) { }; throw new StartFailedException(e); }); } |
Here you can see, that every source type needs a special handling for sending. Here e.g. a callback object (DefaultConsumer) is defined in RabbitMQ that calls fireProcess.
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These methode are defined in the interface ITransportHandlerListener that is implemented by IProtocolHandler, the basic interface for ProtocolHandler.
Registering the handler
Odysseus is OSGi based and all the handler are implemented as declartive services.
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