CODEWITHSUNDEEP
springreactive-programmingspring-webfluxproject-reactor
Viraj
Viraj

Reputation: 5411

Reactive programming how to implement dependent result

I'm trying to use reactive pattern REST service using spring boot. I have setup the code and it's working to save item in Cassandara database. Now I have the following requirement to write in reactive way:

If item is not found in database save the item. If Item is present throw exception.

I have been trying to figure out how do such logic in reactive manner. Since I'm beginner in this field, it's hard to get the concept. Following is my approach:

@Override
public Mono<String> createItem(ItemCreateParam itemCreateParam) {
    //This check if item exits in database.
    Mono<Boolean> byName = reactiveItemRepository.existsById(itemCreateParam.getName());

    //This save the item and return the id (i.e name)
    return Mono.just(itemCreateParam)
            .flatMap(item -> convert(item))
            .log()
            .flatMap(t -> reactiveTemplateRepository.save(t))
            .map(t-> t.getName());
}

How to combine these two in a reactive way?

Upvotes: 0

Views: 1820

Answers (1)

MuratOzkan
MuratOzkan

Reputation: 2750

Just check the result of existsWithId(). This is how I would implement that:

@Override
public Mono<String> createItem(ItemCreateParam itemCreateParam) {
    return reactiveItemRepository.existsById(itemCreateParam.getName())
           .doOnNext(exists -> {
                if (exists) {
                     throw new AppException(ErrorCode.ITEM_EXISTS);
                }
           })
          .flatMap(exists -> convert(item))
          .flatMap(converted -> reactiveTemplateRepository.save(converted))
          .map(saved -> saved.getName());
}

Note that AppException type could be anything else, but it should extend RuntimeException.

Upvotes: 3

Related Questions