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Sunday, August 15, 2010

(JMS) Sending Large Messages to Queue

public class LargeMessageExample
{
public static void main(final String[] args)
{
new LargeMessageExample().run(args);
}
private final long FILE_SIZE = 10L * 1024 * 1024 * 1024; // 10 GiB message
@Override
public boolean runExample() throws Exception
{
Connection connection = null;
InitialContext initialContext = null;\
try
{
// Step 1. Create an initial context to perform the JNDI lookup.
initialContext = getContext(0);
// Step 2. Perfom a lookup on the queue
Queue queue = (Queue)initialContext.lookup("/queue/exampleQueue");
// Step 3. Perform a lookup on the Connection Factory. This ConnectionFactory has a special attribute set on
// it.
// Messages with more than 10K are considered large
ConnectionFactory cf = (ConnectionFactory)initialContext.lookup("/ConnectionFactory");
// Step 4. Create the JMS objects
connection = cf.createConnection();
Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
MessageProducer producer = session.createProducer(queue);
// Step 5. Create a huge file - this will form the body of the message we will send.
File fileInput = new File("huge_message_to_send.dat");
createFile(fileInput, FILE_SIZE);

// Step 6. Create a BytesMessage
BytesMessage message = session.createBytesMessage();

// Step 7. We set the InputStream on the message. When sending the message will read the InputStream
// until it gets EOF. In this case we point the InputStream at a file on disk, and it will suck up the entire
// file, however we could use any InputStream not just a FileInputStream.
FileInputStream fileInputStream = new FileInputStream(fileInput);
BufferedInputStream bufferedInput = new BufferedInputStream(fileInputStream);

message.setObjectProperty("JMS_HQ_InputStream", bufferedInput);

System.out.println("Sending the huge message.");

// Step 9. Send the Message
producer.send(message);

System.out.println("Large Message sent");

System.out.println("Stopping server.");

// Step 10. To demonstrate that that we're not simply streaming the message from sending to consumer, we stop
// the server and restart it before consuming the message. This demonstrates that the large message gets
// persisted, like a
// normal persistent message, on the server. If you look at ./build/data/largeMessages you will see the
// largeMessage stored on disk the server

connection.close();

initialContext.close();

stopServer(0);

// Give the server a little time to shutdown properly
Thread.sleep(5000);

startServer(0);

System.out.println("Server restarted.");

// Step 11. Now the server is restarted we can recreate the JMS Objects, and start the new connection

initialContext = getContext(0);

queue = (Queue)initialContext.lookup("/queue/exampleQueue");

cf = (ConnectionFactory)initialContext.lookup("/ConnectionFactory");

connection = cf.createConnection();

session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);

MessageConsumer messageConsumer = session.createConsumer(queue);

connection.start();

System.out.println("Receiving message.");

// Step 12. Receive the message. When we receive the large message we initially just receive the message with
// an empty body.
BytesMessage messageReceived = (BytesMessage)messageConsumer.receive(120000);

System.out.println("Received message with: " + messageReceived.getBodyLength() +
" bytes. Now streaming to file on disk.");

// Step 13. We set an OutputStream on the message. This causes the message body to be written to the
// OutputStream until there are no more bytes to be written.
// You don't have to use a FileOutputStream, you can use any OutputStream.
// You may choose to use the regular BytesMessage or
// StreamMessage interface but this method is much faster for large messages.

File outputFile = new File("huge_message_received.dat");

FileOutputStream fileOutputStream = new FileOutputStream(outputFile);

BufferedOutputStream bufferedOutput = new BufferedOutputStream(fileOutputStream);

// Step 14. This will save the stream and wait until the entire message is written before continuing.
messageReceived.setObjectProperty("JMS_HQ_SaveStream", bufferedOutput);

fileOutputStream.close();

System.out.println("File streamed to disk. Size of received file on disk is " + outputFile.length());

return true;
}
finally
{
// Step 12. Be sure to close our resources!
if (initialContext != null)
{
initialContext.close();
}

if (connection != null)
{
connection.close();
}
}
}

private void createFile(final File file, final long fileSize) throws FileNotFoundException, IOException
{
FileOutputStream fileOut = new FileOutputStream(file);
BufferedOutputStream buffOut = new BufferedOutputStream(fileOut);
byte[] outBuffer = new byte[1024 * 1024];
for (long i = 0; i < fileSize; i += outBuffer.length)
{
buffOut.write(outBuffer);
}
buffOut.close();
}

}

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