How to convert Mono<List> object to simple List object in java?

Question

I am trying to create a POST API using JAVA web-flux. In this API I want to create a list of string and make a database call to get Mono<List> as a response but when I am trying to convert Mono<List> to simple list object using block() I'm getting below response:

{
    "code": 500,
    "message": "block()/blockFirst()/blockLast() are blocking, which is not supported in thread reactor-http-nio-8"
}

How can I convert Mono object to simple List object?

I'm using below code:

List<String> paymentInstrumentIdList = paymentInstrumentRequest.getPaymentInstruments().stream().map(PaymentInstrumentData::getPaymentInstrumentId).collect(Collectors.toList());
Mono<List<PaymentInstrument>> paymentInstrumentList = paymentInstrumentRepository.getByPartitionKey(partitionKey.toString(), DocType.PAYMENT_INSTRUMENT, paymentInstrumentIdList);
return ResponseEntity.ok(responseMapper.getResponseAsClass(graphQlQueryController.queryPaymentInstrumentsByPaymentInstrumentId(baseHeaders, personId, membershipId, paymentInstrumentList.block()), Wallet.class, "Wallet"));

Does this answer your question? Spring Webflux throws a "block()/blockFirst()/blockLast() are blocking, which is not supported in thread reactor-http-nio-2" — Toerktumlare
– Toerktumlare, Commented Dec 31, 2020 at 6:42

Toerktumlare · Accepted Answer · 2020-12-31 06:36:15Z

4

The entire purpose with webflux applications is that you cannot block

what you are looking for is the flatMap function.

return paymentInstrumentRepository.getByPartitionKey(
    partitionKey.toString(), 
    DocType.PAYMENT_INSTRUMENT, paymentInstrumentIdList)
    .flatmap(list -> {
        return return ServerResponse.ok().body(responseMapper.getResponseAsClass(
    graphQlQueryController.queryPaymentInstrumentsByPaymentInstrumentId(
        baseHeaders, 
        personId, 
        membershipId, 
        list);
    };

This is basic knowledge in webflux i suggest you read the official reactor documentation getting started so you understand the basics and the purpose.

The answer is written on mobile and not tested.

Here is also a getting started tutorial

edited Dec 31, 2020 at 6:36

answered Dec 30, 2020 at 20:25

Toerktumlare

15.1k4 gold badges41 silver badges63 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Jay Desai Over a year ago

Getting error on build() method - java: cannot find symbol symbol: method build() location: class java.lang.object

Toerktumlare Over a year ago

it was written on mobile and not tested so i removed the code, and not to be used to just copy and paste, you get the gist and can look up into the documentation how to return a correct server response

Collectives™ on Stack Overflow

How to convert Mono<List> object to simple List object in java?

1 Answer 1

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related