HL7 client

[John DeStefano]

Hi,

We are working on HL7 connectivity for the JBoss ESB. We have implemented a
simple frame based server in netty to receive HL7 messages using MLLP
protocol. We are working on the client side now. The client initiates a
session with the server and sends an HL7 formatted message to the server.
The server responds with an ACK message which indicates that the message was
received and a code tells the status of the message.

Out issue is around how to synchronize the sending of the message with the
receiving of an ACK. Currently we send a message as follows:

// Sends message
lastWriteFuture =
channel.write(message.getBody().get(Body.DEFAULT_LOCATION));

// wait for it t complete
completed =
lastWriteFuture.awaitUninterruptibly(responseReceiveTimeoutMillis);

If the send completed ok the we wait for the response:

while (true) {
	if (!channel.isConnected()) {
	     throw new Exception("ACK channel has been closed.");
	}
				
	// Read the ChannelLocal variable.
	// This is where we put the ack message.
	// See HL7ClientUpStreamHandler
	// If the clientACK is not null put it in the message
	// Remove the channel from the ChannelLocal variable 
	// and wait for the next one
	String ack = ClientAckState.clientACK.get(channel);
	if (ack != null) {
		ClientAckState.clientACK.remove(channel);
		message.getBody().add(ackLocation, ack);
		break;
	}
}

In the SimpleChannelUpStreamHandler we put the received ACK in a
ChannelLocal variable:

public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) {
      if (e.getMessage() instanceof String) {
	     ClientAckState.clientACK.set(e.getChannel(), (String) e.getMessage());
      }
}

Is this the right way to handle the synchronization of sending a message and
wating for the reply?

Thanks


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