Filter, Custom Filter 코드 문서 및 코드 작성

document/gateway/gateway_filter.md

@@ -0,0 +1,220 @@
+이번 장에서는 [Spring Cloud Gateway - 구성](https://imprint.tistory.com/215) 에 이어 직접 API Gateway에 Filter를 적용하는 방법들에 대해서 알아본다.
+모든 소스 코드는 [깃허브 (링크)](https://github.com/roy-zz/spring-cloud) 에 올려두었다.
+
+---
+
+### 자바 코드로 적용
+
+1. Gateway 모듈에 구성을 위한 FilterConfig 클래스 파일을 생성한다.
+
+"/test-server-1/**" 경로로 들어오는 요청의 헤더에 "test-server-1-request" 키와 "test-server-1-request-header" 값을 가지는 헤더를 추가하고 TEST-SERVER-1 이라는 이름을 가진 애플리케이션에 리다이렉트 한다.
+"/test-server-2/**" 경로로 들어오는 요청의 헤더에 "test-server-2-request" 키와 "test-server-2-request-header" 값을 가지는 헤더를 추가하고 TEST-SERVER-2 라는 이름을 가진 애플리케이션에 리다이렉트 한다.
+
+```java
+@Configuration
+public class FilterConfig {
+    @Bean
+    public RouteLocator gatewayRoutes(RouteLocatorBuilder builder) {
+        return builder.routes()
+                .route(r -> r.path("/test-server-1/**")
+                            .filters(f -> f.addRequestHeader("test-server-1-request", "test-server-1-request-header")
+                                            .addResponseHeader("test-server-1-response", "test-server-1-response-header"))
+                        .uri("lb://TEST-SERVER-1"))
+                .route(r -> r.path("/test-server-2/**")
+                            .filters(f -> f.addRequestHeader("test-server-2-request", "test-server-2-request-header")
+                                            .addResponseHeader("test-server-2-response", "test-server-2-response-header"))
+                        .uri("lb://TEST-SERVER-2"))
+                .build();
+    }
+}
+```
+
+2. Eureka Client의 컨트롤러를 수정한다.
+
+헤더의 정보를 출력하도록 test-server1, test-server2 모듈의 컨트롤러를 수정한다.
+
+**test-server1**
+```java
+@Slf4j
+@RestController
+@RequestMapping(value = "/test-server-1")
+public class TestController {
+    @GetMapping("/welcome")
+    public String welcome(@RequestHeader("test-server-1-request") String requestHeader) {
+        log.info("{}", requestHeader);
+        return "Welcome to the Test Server - 1";
+    }
+}
+```
+
+**test-server2**
+```java
+@Slf4j
+@RestController
+@RequestMapping(value = "/test-server-2")
+public class TestController {
+    @GetMapping("/welcome")
+    public String welcome(@RequestHeader("test-server-2-request") String requestHeader) {
+        log.info("{}", requestHeader);
+        return "Welcome to the Test Server - 2";
+    }
+}
+```
+
+브라우저를 켜고 localhost:8000/test-server-1/welcome과 localhost:8000/test-server-2/welcome에 접속해본다.
+각 모듈의 출력 결과는 아래와 같다.
+**test-server1**
+```bash
+INFO 85192 --- [o-auto-1-exec-1] c.r.s.t.controller.TestController        : test-server-1-request-header
+```
+**test-server2**
+```bash
+INFO 85202 --- [o-auto-1-exec-1] c.r.s.t.controller.TestController        : test-server-2-request-header
+```
+
+Response 헤더에도 정상적으로 입력되었는지 브라우저에서 개발자 모드를 실행시키고 확인해본다.
+
+![](image/check-custom-header.png)
+
+만약 자바 코드로 filter를 적용하고 싶지 않다면?!
+아래와 같이 application.yml 파일을 수정해서 필터를 적용해도 동일하게 작동한다.
+
+```yaml
+spring:
+  application:
+    name: gateway-service
+  cloud:
+    gateway:
+      routes:
+        - id: test-server-1
+          uri: lb://TEST-SERVER-1
+          predicates:
+            - Path=/test-server-1/**
+          filters:
+            - AddRequestHeader=test-server-1-request, test-server-1-request-header
+            - AddResponseHeader=test-server-1-response, test-server-1-response-header
+        - id: test-server-2
+          uri: lb://TEST-SERVER-2
+          predicates:
+            - Path=/test-server-2/**
+          filters:
+            - AddRequestHeader=test-server-2-request, test-server-2-request-header
+            - AddResponseHeader=test-server-2-response, test-server-2-response-header
+```
+
+---
+
+### Custom Filter
+
+1. CustomFilter 클래스를 생성한다.
+
+AbstractGatewayFilterFactory를 상속받은 클래스를 생성한다.
+apply메서드를 확인해보면 요청처리 전에 필터를 처리하는 부분과 요청처리 후에 필터를 처리하는 부분이 나뉘어 있는 것을 확인할 수 있다.
+
+```java
+@Slf4j
+@Component
+public class CustomFilter extends AbstractGatewayFilterFactory<CustomFilter.Config> {
+    public CustomFilter() {
+        super(Config.class);
+    }
+    @Override
+    public GatewayFilter apply(Config config) {
+        return (exchange, chain) -> {
+            // Pre process start ====================================================
+            ServerHttpRequest request = exchange.getRequest();
+            ServerHttpResponse response = exchange.getResponse();
+            log.info("Custom pre process filter: request uri -> {}", request.getId());
+            // Pre process end =======================================================
+            // Post process start =======================================================
+            return chain.filter(exchange).then(Mono.fromRunnable(() -> {
+                log.info("Custom post process filter: response code -> {}", response.getStatusCode());
+            }));
+            // Post process end =======================================================
+        };
+    }
+    public static class Config {
+        // Put the configuration properties
+    }
+}
+```
+
+2. application.yml 수정
+
+우리가 생성한 CustomFilter로 등록될 수 있도록 filters 항목에 CustomFilter를 등록한다.
+
+```yaml
+spring:
+  application:
+    name: gateway-service
+  cloud:
+    gateway:
+      routes:
+        - id: test-server-1
+          uri: lb://TEST-SERVER-1
+          predicates:
+            - Path=/test-server-1/**
+          filters:
+            - CustomFilter
+        - id: test-server-2
+          uri: lb://TEST-SERVER-2
+          predicates:
+            - Path=/test-server-2/**
+          filters:
+            - CustomFilter
+```
+
+3. 유레카 클라이언트의 컨트롤러를 수정한다.
+
+Filter 연동을 위해 수정한 부분은 없으며 단지 이전 테스트와 컨트롤러가 겹치는 것을 방지하기 위함이다.
+
+**test-server-1**
+```java
+@Slf4j
+@RestController
+@RequestMapping(value = "/test-server-1")
+public class TestController {
+    @GetMapping("/custom-filter")
+    public String customFilter() {
+        return "Custom filter with test server 1";
+    }
+}
+```
+
+**test-server-2**
+```java
+@Slf4j
+@RestController
+@RequestMapping(value = "/test-server-2")
+public class TestController {
+    @GetMapping("/custom-filter")
+    public String customFilter() {
+        return "Custom filter with test server 2";
+    }
+}
+```
+
+4. 정상작동 확인
+
+브라우저를 켜고 localhost:8000/test-server-1/custom-filter와 localhost:8000/test-server-2/custom-filter에 접속해본다.
+출력된 결과는 아래와 같다.
+
+```bash
+c.r.s.gateway.filter.CustomFilter        : Custom pre process filter: request uri -> baf12948-2
+c.r.s.gateway.filter.CustomFilter        : Custom post process filter: response code -> 200 OK
+c.r.s.gateway.filter.CustomFilter        : Custom pre process filter: request uri -> baf12948-3
+c.r.s.gateway.filter.CustomFilter        : Custom post process filter: response code -> 200 OK
+```
+
+정상적으로 우리가 원하는 결과가 출력되는 것을 확인할 수 있다.
+~~(설마 c.r.s가 com.roy.springcloud의 약자인가...왜 처음알았지)~~
+
+---
+
+
+
+
+
+---
+
+참고한 강의: https://www.inflearn.com/course/%EC%8A%A4%ED%94%84%EB%A7%81-%ED%81%B4%EB%9D%BC%EC%9A%B0%EB%93%9C-%EB%A7%88%EC%9D%B4%ED%81%AC%EB%A1%9C%EC%84%9C%EB%B9%84%EC%8A%A4

gateway/build.gradle

@@ -5,6 +5,8 @@ ext {
 dependencies {
     implementation 'org.springframework.cloud:spring-cloud-starter-gateway'
     implementation 'org.springframework.cloud:spring-cloud-starter-netflix-eureka-client'
+    compileOnly 'org.projectlombok:lombok'
+    annotationProcessor 'org.projectlombok:lombok'
     testImplementation 'org.springframework.boot:spring-boot-starter-test'
 }
 

gateway/src/main/java/com/roy/springcloud/gateway/config/FilterConfig.java

@@ -0,0 +1,21 @@
+package com.roy.springcloud.gateway.config;
+
+import org.springframework.cloud.gateway.route.RouteLocator;
+import org.springframework.cloud.gateway.route.builder.RouteLocatorBuilder;
+
+// @Configuration
+public class FilterConfig {
+    // @Bean
+    public RouteLocator gatewayRoutes(RouteLocatorBuilder builder) {
+        return builder.routes()
+                .route(r -> r.path("/test-server-1/**")
+                            .filters(f -> f.addRequestHeader("test-server-1-request", "test-server-1-request-header")
+                                            .addResponseHeader("test-server-1-response", "test-server-1-response-header"))
+                        .uri("lb://TEST-SERVER-1"))
+                .route(r -> r.path("/test-server-2/**")
+                            .filters(f -> f.addRequestHeader("test-server-2-request", "test-server-2-request-header")
+                                            .addResponseHeader("test-server-2-response", "test-server-2-response-header"))
+                        .uri("lb://TEST-SERVER-2"))
+                .build();
+    }
+}

gateway/src/main/java/com/roy/springcloud/gateway/filter/CustomFilter.java

@@ -0,0 +1,37 @@
+package com.roy.springcloud.gateway.filter;
+
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.cloud.gateway.filter.GatewayFilter;
+import org.springframework.cloud.gateway.filter.factory.AbstractGatewayFilterFactory;
+import org.springframework.http.server.reactive.ServerHttpRequest;
+import org.springframework.http.server.reactive.ServerHttpResponse;
+import org.springframework.stereotype.Component;
+import reactor.core.publisher.Mono;
+
+@Slf4j
+@Component
+public class CustomFilter extends AbstractGatewayFilterFactory<CustomFilter.Config> {
+    public CustomFilter() {
+        super(Config.class);
+    }
+
+    @Override
+    public GatewayFilter apply(Config config) {
+        return (exchange, chain) -> {
+            // Pre process start ====================================================
+            ServerHttpRequest request = exchange.getRequest();
+            ServerHttpResponse response = exchange.getResponse();
+            log.info("Custom pre process filter: request uri -> {}", request.getId());
+            // Pre process end =======================================================
+            // Post process start =======================================================
+            return chain.filter(exchange).then(Mono.fromRunnable(() -> {
+                log.info("Custom post process filter: response code -> {}", response.getStatusCode());
+            }));
+            // Post process end =======================================================
+        };
+    }
+
+    public static class Config {
+        // Put the configuration properties
+    }
+}

gateway/src/main/resources/application.yml

@@ -18,7 +18,15 @@ spring:
           uri: lb://TEST-SERVER-1
           predicates:
             - Path=/test-server-1/**
+          filters:
+            # - AddRequestHeader=test-server-1-request, test-server-1-request-header
+            # - AddResponseHeader=test-server-1-response, test-server-1-response-header
+            - CustomFilter
         - id: test-server-2
           uri: lb://TEST-SERVER-2
           predicates:
             - Path=/test-server-2/**
+          filters:
+            # - AddRequestHeader=test-server-2-request, test-server-2-request-header
+            # - AddResponseHeader=test-server-2-response, test-server-2-response-header
+            - CustomFilter

test-server1/src/main/java/com/roy/springcloud/testserver1/controller/TestController.java

@@ -1,16 +1,25 @@
 package com.roy.springcloud.testserver1.controller;
 
+import lombok.extern.slf4j.Slf4j;
 import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestHeader;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RestController;
 
+@Slf4j
 @RestController
 @RequestMapping(value = "/test-server-1")
 public class TestController {
 
     @GetMapping("/welcome")
-    public String welcome() {
+    public String welcome(@RequestHeader("test-server-1-request") String requestHeader) {
+        log.info("{}", requestHeader);
         return "Welcome to the Test Server - 1";
     }
 
+    @GetMapping("/custom-filter")
+    public String customFilter() {
+        return "Custom filter with test server 1";
+    }
+
 }

test-server2/src/main/java/com/roy/springcloud/testserver2/controller/TestController.java

@@ -1,16 +1,25 @@
 package com.roy.springcloud.testserver2.controller;
 
+import lombok.extern.slf4j.Slf4j;
 import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestHeader;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RestController;
 
+@Slf4j
 @RestController
 @RequestMapping(value = "/test-server-2")
 public class TestController {
 
     @GetMapping("/welcome")
-    public String welcome() {
+    public String welcome(@RequestHeader("test-server-2-request") String requestHeader) {
+        log.info("{}", requestHeader);
         return "Welcome to the Test Server - 2";
     }
 
+    @GetMapping("/custom-filter")
+    public String customFilter() {
+        return "Custom filter with test server 2";
+    }
+
 }