Rewrite service request using optionals

Question

I want to rewrite the code below using Optionals ( I do not control jpaConnector ):

public boolean deleteLockStatus() {

    IMdss service = jpaConnector.getMdssService();
    if ( service == null ) {
        return false;
    }

    ServiceResponse response = null;
    try {
        response = service.deleteLockStatus();
    } catch (Exception e) {
        e.printStackTrace();
    }

    if ( response == null ) {
        return false;
    }
    if ( response.isError() ) {
        return false;
    }
    return true;
}

I have achievied this so far:

public boolean deleteLockStatus() {

    Optional<IMdss> service = Optional.ofNullable(jpaConnector.getMdssService());

    if (!service.isPresent()) { return false; }


    Optional<ServiceResponse> response = Optional.empty();
    try {
        response = Optional.ofNullable(service.get().deleteLockStatus());
        if ( response.isPresent() == false || response.get().isError() ) {
            return false;
        }
    } catch (Exception e) {
        e.printStackTrace();
        return false;
    }

    return true;
}

Is there a better and more native java 8 way? Thank you!!!

Answer 1

We start with an Optional<Service>, flat map that to an Optional<ServiceResponse> (using the regular map function would give us Optional<Optional<ServiceResponse>>), then map that to an Optional<Boolean>.

The Optional<Boolean> represents success or failure of the response. If we don't have a value here, an exception was thrown so we return false with orElse(false).

It's a shame about the checked exception and having to print the stack trace, or else it could be a lot more concise.

public boolean deleteLockStatus() {
    return Optional.ofNullable(jpaConnector.getMdssService())
        .flatMap(service -> {
            try {
                return Optional.ofNullable(service.deleteLockStatus());
            }
            catch(Exception e) {
                e.printStackTrace();
                return Optional.empty();
            }
        })
        .map(ServiceResponse::isError)
        .orElse(false);
}

Side note: catching Exception is usually a bad idea. You should be as specific as possible. Consider using this syntax if there are multiple possible exceptions which may be thrown.

---

As mentioned in the comments by Federico, you can replace the flatMap with this slight simplification if you don't mind using null. I would personally prefer the version above.

.map(service -> {
     try {
         return service.deleteLockStatus();
     }
     catch(Exception e) {
         e.printStackTrace();
         return null;
     }
 })