How to handle errors in Spring reactor Mono or Flux?

Question

I have below code retuning Mono:

try {
    return userRepository.findById(id)  // step 1
        .flatMap(user -> barRepository.findByUserId( u         


        

Answer 1

I think the first error is in the title: "Mono or Flux" is not related with the error handling.

• Mono can only emit one item at the most (streams one element)
• Flux can emit more complex stuff (i.e. List)

To handle errors you can follow this example:

return webClient.get()
                .uri(url)
                .retrieve()
                .bodyToMono(ModelYouAreRetrieving.class)
                .doOnError(throwable -> logger.error("Failed for some reason", throwable))
                .onErrorReturn(new ModelYouAreRetrieving(...))
                .block();