HAPI HL7v2

The Responder class performs the responding role in an HL7v2 message exchange (acting as a server). It receives an incoming message, identifies the appropriate application to handle it via an ApplicationRouter, and returns a response message.

Key Characteristics:

• It follows HL7's original mode processing rules.
• It currently does not support enhanced mode, two-phase reply, continuation messages, or batch processing.
• It requires an ApplicationRouter to be configured via setApplicationRouter to determine how messages are routed to specific software applications.

// Conceptual usage pattern
Socket inboundSocket = serverSocket.accept();
Responder responder = new Responder(inboundSocket);
responder.setApplicationRouter(myApplicationRouter);

// The processMessage method is protected and typically called by the underlying connection logic
String response = responder.processMessage(incomingMessageString);

The ConnectionData class is used to encapsulate the configuration and metadata required for a TCP/IP connection to a remote HL7 server. It defines the host, ports, security settings (TLS), parsing logic, and the underlying protocol.

Key configuration parameters include:

• host: The remote server hostname or IP address.
• port / outboundPort: The primary port for the connection.
• port2 / inboundPort: An additional port (used in specific connection scenarios).
• tls: A boolean indicating whether to use TLS encryption.
• parser: The Parser instance used to handle HL7 messages.
• protocol: The LowerLayerProtocol implementation (e.g., MLLP).
• connectionTimeout: An optional integer specifying the connection timeout.
• socketFactory: A custom SocketFactory for managing socket creation; if not provided, a StandardSocketFactory is used.

// Example: Creating a basic connection configuration
ConnectionData config = new ConnectionData(
    "localhost", 
    4556, 
    myParser, 
    myProtocol
);

// Example: Creating a TLS-enabled connection with a timeout
ConnectionData tlsConfig = new ConnectionData(
    "remote-server.com", 
    4556, 
    myParser, 
    myProtocol, 
    true, 
    5000
);

The MllpEncoder class is used to wrap an HL7 message string into the Minimum Lower Layer Protocol (MLLP) format and write it to an OutputStream.

An MLLP frame consists of a start byte (MllpConstants.START_BYTE), the message payload, and two end bytes (MllpConstants.END_BYTE1 and MllpConstants.END_BYTE2). The encoder ensures the entire message is sent in a single frame to prevent fragmentation issues.

To use this, you must provide a Charset and a boolean flag omitBOM (to determine if the Byte Order Mark should be removed) during instantiation.

// Note: MllpEncoder is package-private in the source, 
// so usage assumes access within the ca.uhn.hl7v2.llp package

MllpEncoder encoder = new MllpEncoder(StandardCharsets.UTF_8, true);
String hl7Message = "MSH|^~\\|...";
OutputStream outputStream = // your destination stream;

encoder.putMessage(hl7Message, outputStream);