project reactor - WebFlux chain various actions based on different results - Stack Overflow

I have this chain of actions to orchestrate:

• A) check if user has already paid boolean checkUserPayment(Long userId)
• B) if above A) is true, then proceed with UserInformation fetchUserInformationFromAPI(Long userID)
• B) if above A) is false, then break immediatly and do return Mono.just(PaymentResponse.alreadyPaid(userId))
• C) if UserInformation fetchUserInformationFromAPI(Long userID) yields a value then
• D) initiate Payment via PaymentResponse sendPaymentRequest(PaymentRequest paymentRequest)
• E) if C) does not yield an user or somehow breaks, don't go to D) instead return Mono.just(PaymentResponse.Error(throwable)

So all in all i want a method like:
Mono<PaymentResponse initiatePayment(Long userID) which orchestrates the above steps ...

Does Mono support such scenarios?

Thanks for your input!

EDIT: Based on the first answer, i want a single method, because all the subsequent steps are methods too. So in a non reactive way, it would look like this:

public PaymentResponse(Long userId){
    if(checkUserPayment(userId){
       return PaymentResponse.AlreadyPaid(userId);
    }
    UserInformation ui = fetchUserInformationFromAPI(Long userID);
    if(ui == null) return PaymentResponse.Error(userId)
    PaymentResponse pr = sendPaymentRequest(PaymentRequest paymentRequest);
    if(pr == null) return PaymentResponse.Error(userId);
    return pr;
}

I have this chain of actions to orchestrate:

• A) check if user has already paid boolean checkUserPayment(Long userId)
• B) if above A) is true, then proceed with UserInformation fetchUserInformationFromAPI(Long userID)
• B) if above A) is false, then break immediatly and do return Mono.just(PaymentResponse.alreadyPaid(userId))
• C) if UserInformation fetchUserInformationFromAPI(Long userID) yields a value then
• D) initiate Payment via PaymentResponse sendPaymentRequest(PaymentRequest paymentRequest)
• E) if C) does not yield an user or somehow breaks, don't go to D) instead return Mono.just(PaymentResponse.Error(throwable)

So all in all i want a method like:
Mono<PaymentResponse initiatePayment(Long userID) which orchestrates the above steps ...

Does Mono support such scenarios?

Thanks for your input!

EDIT: Based on the first answer, i want a single method, because all the subsequent steps are methods too. So in a non reactive way, it would look like this:

public PaymentResponse(Long userId){
    if(checkUserPayment(userId){
       return PaymentResponse.AlreadyPaid(userId);
    }
    UserInformation ui = fetchUserInformationFromAPI(Long userID);
    if(ui == null) return PaymentResponse.Error(userId)
    PaymentResponse pr = sendPaymentRequest(PaymentRequest paymentRequest);
    if(pr == null) return PaymentResponse.Error(userId);
    return pr;
}

• spring-webflux
• project-reactor

Share Improve this question Follow edited Jan 9 at 6:01 Thomas Lang asked Jan 8 at 12:49 Thomas LangThomas Lang 1,49533 gold badges2222 silver badges3939 bronze badges

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1 Answer 1

Sorted by: Reset to default 1

Reactive supports such type of scenarios. A general advice would be to split the execution in smaller methods. have a look at above sample.

public Mono<PaymentResponse> initiatePayment(Long userID){
    return Mono.fromSupplier(()->userID)
        .map(id->checkUserPayment(id))
        .flatMap(pending->pending ? someOtherOperation(userID): Mono.just(PaymentResponse.alreadyPaid(userId)));
}

public Mono<PaymentResponse> someOtherOperation(Long userID){
    return Mono.fromSupplier(()->userID)
        .map(id->fetchUserInformationFromAPI(id))
        .map(userInfo->sendPaymentRequest(PaymentRequest.from(userInfo)))
        .onErrorResume(throwable->Mono.just(PaymentResponse.Error(throwable)));
}