Spring Boot 3 + RestClient + Apache HttpClient 설정 방법

build.gradle에 의존성 추가

• 최신 http client 5 버전을 추가한다.

  // Apache HttpClient 5
  implementation 'org.apache.httpcomponents.client5:httpclient5:5.4.3'
  

RestClientConfig 설정

• HttpClient를 Bean으로 등록하기 위한 Config 클래스
• Apache HTTP Components를 사용하는 경우, RequestFactory를 HttpComponentsClientHttpRequestFactory로 사용 (공식 문서)
  • 외부 라이브러리 없이 RestClient를 사용하는 경우, RequestFactory의 기본값은 SimpleClientHttpRequestFactory 이다.
  • SimpleClientHttpRequestFactory는 다양한 속성이 지원되지 않고, connection pool 역시 지원 안됨.
• 설정 예시

  @Slf4j
  @Configuration
  public class TMDBRestClientConfig {
  
      private final String API_READ_ACCESS_TOKEN;
      private final String API_KEY;
  
      public TMDBRestClientConfig(
          @Value("${tmdb.api-read-access-token}")
          String API_READ_ACCESS_TOKEN,
          @Value("${tmdb.api-key}")
          String API_KEY
      ) {
          this.API_READ_ACCESS_TOKEN = API_READ_ACCESS_TOKEN;
          this.API_KEY = API_KEY;
      }
  
      private static final ObjectMapper objectMapper = new ObjectMapper();
      private static final String BASE_URL = "https://api.themoviedb.org/3";
      private static final int CONNECTION_TIMEOUT = 5;
      private static final int READ_TIMEOUT = 25;
      private static final int MAX_TOTAL_CONNECTIONS = 100;
      private static final int MAX_PER_ROUTE = 20;
  
      @Bean
      public TMDBRestClient tmdbRestClient() {
          return HttpServiceProxyFactory
              .builderFor(RestClientAdapter.create(getTMDBRestClient()))
              .build()
              .createClient(TMDBRestClient.class);
      }
  
      private RestClient getTMDBRestClient() {
          return RestClient.builder()
              .baseUrl(BASE_URL)
              .defaultHeaders(httpHeaders -> {
                  httpHeaders.add(HttpHeaders.AUTHORIZATION, getAuthorizationHeaderValue());
                  httpHeaders.setContentType(MediaType.APPLICATION_JSON);
              })
              .requestFactory(getClientHttpRequestFactory())
              .defaultStatusHandler(HttpStatusCode::is4xxClientError, default4xxErrorHandler())
              .defaultStatusHandler(HttpStatusCode::is5xxServerError, default5xxErrorHandler())
              .build();
      }
  
      private String getAuthorizationHeaderValue() {
          return "Bearer " + this.API_READ_ACCESS_TOKEN;
      }
  
      private ClientHttpRequestFactory getClientHttpRequestFactory() {
          return new HttpComponentsClientHttpRequestFactory(createApacheHttpClient());
      }
  
      private HttpClient createApacheHttpClient() {
          RequestConfig requestConfig = RequestConfig.custom()
              .setConnectionRequestTimeout(CONNECTION_TIMEOUT, TimeUnit.SECONDS)
              .setResponseTimeout(READ_TIMEOUT, TimeUnit.SECONDS)
              .build();
  
          PoolingHttpClientConnectionManager connectionManager = new PoolingHttpClientConnectionManager();
          connectionManager.setMaxTotal(MAX_TOTAL_CONNECTIONS); // 전체 커넥션 수 최대값
          connectionManager.setDefaultMaxPerRoute(MAX_PER_ROUTE); // 도메인(호스트) 당 최대 커넥션 수
  
          return HttpClients.custom()
              .setConnectionManager(connectionManager)
              .setDefaultRequestConfig(requestConfig)
              .evictIdleConnections(Timeout.ofSeconds(30)) // 일정 시간 이상 유휴 커넥션 정리 (메모리 누수 방지)
              .build();
      }
  
      private ResponseSpec.ErrorHandler default4xxErrorHandler() {
          return (req, res) -> {
              Map<String, Object> errorBody = getErrorBody(res);
              HttpStatusCode statusCode = res.getStatusCode();
              printErrorLog(statusCode, errorBody);
              switch (statusCode) {
                  case HttpStatus.UNAUTHORIZED ->
                      throw new ApiErrorException(ErrorCode.AUTHENTICATION_FAIL);
                  case HttpStatus.NOT_FOUND -> throw new ApiErrorException(ErrorCode.NOT_FOUND);
                  default -> throw new ApiErrorException(ErrorCode.BAD_REQUEST);
              }
          };
      }
  
      private ResponseSpec.ErrorHandler default5xxErrorHandler() {
          return (req, res) -> {
              Map<String, Object> errorBody = getErrorBody(res);
              HttpStatusCode statusCode = res.getStatusCode();
              printErrorLog(statusCode, errorBody);
              throw new ApiErrorException(ErrorCode.EXTERNAL_SERVER_ERROR);
          };
      }
  
      private Map<String, Object> getErrorBody(ClientHttpResponse res) {
          Map<String, Object> errorBody;
          try {
              errorBody = objectMapper.readValue(
                  res.getBody(),
                  new TypeReference<>() {
                  }
              );
          } catch (Exception e) {
              log.error("Failed to parse TMDBRestClient error response body", e);
              throw new ApiErrorException(ErrorCode.EXTERNAL_SERVER_ERROR);
          }
          return errorBody;
      }
  
      private void printErrorLog(
          HttpStatusCode statusCode,
          Map<String, Object> errorBody
      ) {
          log.error("TMDBRestClient Error Status Code: {}", statusCode.value());
          log.error("TMDBRestClient Error Body: {}", errorBody);
      }
  
  }
  

사용 예제

• 설정한 값에 맞게 Bean 생성 후 서비스 레이어에서 RestClient 인터페이스를 주입하여 사용
• Interface 코드

  @Component
  @HttpExchange
  public interface TMDBRestClient {
  
      @GetExchange(value = "/movie/popular")
      TMDBPopularMoviePageResponse getPopularMovies(
          @RequestParam(name = "language", defaultValue = "ko-KR") String language,
          @RequestParam(name = "page", defaultValue = "1") Integer page
      );
  
  }
  

• Service 코드에서 실제 사용 예시

  @Slf4j
  @Service
  @RequiredArgsConstructor
  public class TMDBService {
  
      private final TMDBRestClient tmdbRestClient;
  
      public PopularMoviePageResponse getPopularMovies(int page) {
          return PopularMoviePageResponse.from(
              tmdbRestClient.getPopularMovies(null, page)
          );
      }
  }