如何让我的服务 object 等到它在 Spring 启动中收到来自外部资源的响应

Question

I am implementing a client application to automate trading tasks in InteractiveBroker(IB) platform. They are providing us with standalone application called TradingWorkStation(TWS) and a library to implement our own client applications. But our client application cannot directly communicate with IB platform on its own, client app has to pass our message to TWS application and TWS handles the communication with the actual IB platform.

IB library provides us with EClientSocket interface, which has methods to communicate with TWS application. But they are asynchronous calls with no responses. When TWS needs to send back responses, it calls EWrapper interface of client application.

Refer to following diagram,

I am using Spring Boot to develop this client application. I have TraderService class which has eClient object as a attribute to communicate with TWS app. And I need to ask for contract details from TWS to initiate the trading process. I need TraderService constructor to continue only of these requested contract details are available.

Refer to TraderService below,

@Service
public class TraderService {
    private final IBEventWrapper eventWrapper;
    private final EClientSocket socket;

    public TraderService() {
        
        this.eventWrapper = new IBEventWrapper();

        this.socket = new EClientSocket(eventWrapper);
        socket.eConnect('localhost', 7497, 1);

        if (socket.isConnected()) {
            logger.info("connected..");
            
            // requesting contract details, but return type is void
            socket.reqContractDetails();

           // continue only if contract results are available ...
        }
    }
}

Notice here, reqContractDetails method does not have a return type, and actual results are received to EWrapper interface implementation.

Refer to EWrapper implementatin below,

public class IBEventWrapper implements EWrapper {
    private final TraderService traderService;

    public IBEventWrapper(TraderService traderService) {
        // trying to pass results back to trader service
        this.traderService = traderService;
    }
    
    // this method is invoked by TWS to return contract results
    @Override
    public void contractDetails(int reqId, ContractDetails contractDetails) {
        logger.info("contractDetails {}", reqId);
    }
}

As seen above, EWrapper methods are invoked by TWS app, when results are available. But I need to pass them back to TraderService constructor.

Is there any approach (may be from Spring boot) to make this happen.

Answer 1

IB TWS API is publish–subscribe based, you will have to make requests and await data to return. I have been using CountDownLatch like this (in your handler class):

  private CountDownLatch latch = new CountDownLatch(1);

  public String getGenericTick() {
    return genericTick;
  }

  public CountDownLatch getLatch() {
    return latch;
  }

  @Override
  public void tickString(TickType tickType, String value) {
    if (tickType == TickType.FUNDAMENTAL_RATIOS) {
      genericTick = value;
      latch.countDown();
    }
  }

Which allows you to know if the data is available or explicitly await for some time (3s is usually enough for anything within a single request):

  var handler = new FundamentalsRatiosDataHandler();

  controller.reqTopMktData(contract, "258", false, false, handler);
    if (!handler
        .getLatch()
        .await(3, TimeUnit.SECONDS)) {
      // failure
    }