WebFlux : 데이터를 찾지 못한 경우 Exception 발생하기

1. Reactive프로그래밍에서 Optional처럼 orElseThrow() 같은 함수를 사용하기 원하는 경우는

  1-1 아래의 findById와 같이 map을 사용하여 데이터가 있는 경우, 적절하게 처리하고

  1-2 switchIfEmpty 함수를 활용하여 에러를 발생시킬 수 있다.

  1-3 findById와 거의 같은 findCommandById함수와 비교하면 차이를 쉽게 알 수 있다.

 

package pe.pilseong.recipe.service;

import org.springframework.stereotype.Service;

import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import pe.pilseong.recipe.command.RecipeCommand;
import pe.pilseong.recipe.converter.RecipeCommandToRecipe;
import pe.pilseong.recipe.converter.RecipeToRecipeCommand;
import pe.pilseong.recipe.domain.Recipe;
import pe.pilseong.recipe.exception.NotFoundException;
import pe.pilseong.recipe.repository.reactive.RecipeReactiveRepository;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

@Service
@RequiredArgsConstructor
@Slf4j
public class RecipeServiceImpl implements RecipeService {

  private final RecipeReactiveRepository recipeReactiveRepository;
  private final RecipeCommandToRecipe recipeConverter;
  private final RecipeToRecipeCommand commandConverter;

  @Override
  public Flux<Recipe> getRecipes() {
    log.debug("getRecipes in RecipeServiceImpl");

    return recipeReactiveRepository.findAll();
  }

  @Override
  public Mono<Recipe> findById(String id) {    
    return recipeReactiveRepository.findById(id).map(fetchedRecipe -> {
      fetchedRecipe.getIngredients().forEach(ingredient-> ingredient.setRecipeId(fetchedRecipe.getId()));
      return fetchedRecipe;
    })
    .switchIfEmpty(Mono.error(new NotFoundException("recipe not found with id :: " + id)));
  }

  @Override
  public Mono<Recipe> save(RecipeCommand command) {
    return recipeReactiveRepository.save(recipeConverter.convert(command));
  }

  @Override
  public Mono<RecipeCommand> findCommandById(String id) {
    Recipe reactiveRecipe = recipeReactiveRepository.findById(id).block();
    if (reactiveRecipe != null) {
      return Mono.just(commandConverter.convert(reactiveRecipe));
    } else {
      throw new NotFoundException("recipe not found with id :: " + id);
    }
  }

  @Override
  public Mono<RecipeCommand> saveRecipeCommand(RecipeCommand command) {
    return recipeReactiveRepository.save(recipeConverter.convert(command))
      .map(commandConverter::convert);
  }

  @Override
  public Mono<Void> deleteById(String id) {
    recipeReactiveRepository.deleteById(id).block();

    return Mono.empty();
  }
}

 

2. 자세한 내용은 StackOverflow에서 다양한 방법으로 잘 설명되어 있다.

 

Correct way of throwing exceptions with Reactor