How to implement simple echo socket service in Spring Integration DSL

Question

Please,
could you help with implementation of a simple, echo style, Heartbeat TCP socket service in Spring Integration DSL? More precisely how to plug Adapter/Handler/Ga

Answer 1

For anyone interested, here is one of the working solutions I made with help from Gary Russell. All credits to Gary Russell. Full project source code here.

Highlights:

• IntegrationFlows: Use only inbound and outbound Gateways.
• No Adapters or Channels needed; no ServiceActivators or Message Gate proxies.
• No need for ScheduledExecutor or Executors; client and server code got significatn
• IntegrationFlows directly calls methods on client class and server class; I like this type of explicit connection.
• Split client class on two parts, two methods: request producing part and response processing part; this way it can be better chained to flows.
• explicitly define clientConnectionFactory/serverConnectionFactory. This way more things can be explicitly configured later.

HeartbeatClientConfig

@Bean
public IntegrationFlow heartbeatClientFlow(
        TcpNetClientConnectionFactory clientConnectionFactory,
        HeartbeatClient heartbeatClient) {
    return IntegrationFlows.from(heartbeatClient::send,  e -> e.poller(Pollers.fixedDelay(Duration.ofSeconds(5))))
            .handle(Tcp.outboundGateway(clientConnectionFactory))
            .handle(heartbeatClient::receive)
            .get();
}

HeartbeatClient

public class HeartbeatClient {
    private final Logger log = LogManager.getLogger(HeartbeatClient.class);

    public GenericMessage send() {
        log.info("Sending Heartbeat");
        return new GenericMessage("status");
    }

    public Object receive(byte[] payload, MessageHeaders messageHeaders) { // LATER: use transformer() to receive String here
        String messageStr = new String(payload);
        if (messageStr.equals("OK")) {
            log.info("Heartbeat OK response received");
        } else {
            log.error("Unexpected message content from server: " + messageStr);
        }
        return null;
    }
}

HeartbeatServerConfig

@Bean
public IntegrationFlow heartbeatServerFlow(
        TcpNetServerConnectionFactory serverConnectionFactory,
        HeartbeatServer heartbeatServer) {
    return IntegrationFlows
            .from(Tcp.inboundGateway(serverConnectionFactory))
            .handle(heartbeatServer::processRequest)
            .get();
}

HeartbeatServer

public class HeartbeatServer {
    private final Logger log = LogManager.getLogger(HeartbeatServer.class);

    public Message processRequest(byte[] payload, MessageHeaders messageHeaders) {
        String messageStr = new String(payload);
        if (messageStr.equals("status")) {
            log.info("Heartbeat received");
            return new GenericMessage<>("OK");
        } else {
            log.error("Unexpected message content from client: " + messageStr);
            return null;
        }

    }
}