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Filter, Custom Filter 코드 문서 및 코드 작성

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2022-04-20 18:46:19 +09:00
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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

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gateway/build.gradle
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@@ -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'
}

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gateway/src/main/java/com/roy/springcloud/gateway/config/FilterConfig.java Normal file
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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();
}
}

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gateway/src/main/java/com/roy/springcloud/gateway/filter/CustomFilter.java Normal file
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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
}
}

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gateway/src/main/resources/application.yml
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@@ -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/**
- 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

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test-server1/src/main/java/com/roy/springcloud/testserver1/controller/TestController.java
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@@ -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";
}
}

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test-server2/src/main/java/com/roy/springcloud/testserver2/controller/TestController.java
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@@ -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";
}
}