Custom Filter

• AbstractGatewayFilterFactory를 상속받아 Custom Filter를 구현할 수 있다.
• Gateway의 Custom Filter를 이용하여 JWT 토큰을 인증 작업을 체크하는 작업등의 작업을 할 수 있다.

CustomFilter 생성 실습

1. Gateway Project 에 CustomFilter class 구현

   @Slf4j
   @Component
   public class CustomFilter extends AbstractGatewayFilterFactory<CustomFilter.Config> {
       public CustomFilter() {
           super(Config.class);
       }
   
       @Override
       public GatewayFilter apply(Config config) {
           // Custom Pre Filter
           return (exchange, chain) -> {
               ServerHttpRequest request = exchange.getRequest();
               ServerHttpResponse response = exchange.getResponse();
   
               log.info("Custom PRE filter: request id -> {}", request.getId());
   
               // Custom Post Filter
               return chain.filter(exchange).then(Mono.fromRunnable(() -> {
                   log.info("Custom POST filter: response code -> {}", response.getStatusCode());
               }));
           };
       }
   
       public static class Config {
           // Put the configuration properties
       }
   }

   • AbstractGatewayFilterFactory를 상속하여 Custom Filter 구현
   • CustomFilter.Config는 Custom Filter의 Configuration 정보 class
   • apply method를 오버 로딩 한뒤 filter 를 구현
   • PRE, POST 필터의 구현 방식 확인

2. application.yml의 gateway filters 에 CustomFilter 등록

   spring:
     application:
       name: api-gateway-service
     cloud:
       gateway:
         routes:
           - id: first-service
             uri: http://localhost:8081/
             predicates:
               - Path=/first-service/**
             filters:
               - AddRequestHeader=first-request, first-request-header2
               - AddResponseHeader=first-response, first-response-header2
               - CustomFilter # 추가
           - id: second-service
             uri: http://localhost:8082/
             predicates:
               - Path=/second-service/**
             filters:
               - AddRequestHeader=second-request, second-request-header2
               - AddResponseHeader=second-response, second-response-header2
               - CustomFilter # 추가

3. Service Project에 Test를 위한 API 생성

   First-Service, Second-Service의 Controller에 다음과 같은 API를 추가

   @GetMapping("/check")
   public String check() {
       return "Hi, there. This is a message from Second Service";
   }

4. Custom Filter 작동 테스트

   http://localhost:8000/first-service/check

   w.duckbill.gateway.filter.CustomFilter   : Custom PRE filter: request id -> 994c106b-5
   w.duckbill.gateway.filter.CustomFilter   : Custom POST filter: response code -> 200 OK

   • 로그를 확인해 보면 PRE, POST Filter가 작동됨이 확인 가능