Spring Cloud Openfeign
RECOMMEND POSTS BEFORE THIS
1. Spring Cloud Openfeign
Spring Cloud Openfeign API Reference
Feign is a declarative web service client. It makes writing web service clients easier.
MSA(MicroService Architecture)를 지원하는 스프링 클라우드(spring cloud) 프로젝트들 중 하나입니다. 서비스들 사이의 API 요청, 응답을 쉽게 할 수 있도록 돕는 라이브러리입니다. 간단한 예제 코드를 통해 사용 방법을 살펴보겠습니다.
2. Practice
2.1. Context of Practice
다음과 같은 상황을 만들어 사용해보았습니다.
- 사용자는
서비스A의/health경로로 API 요청을 수행합니다. 서비스A는/health요청을 받으면서비스B로 API 요청을 수행합니다.서비스B는 자신의 상태를 응답합니다.서비스A는서비스B응답과 자신의 상태를 함께 응답합니다.- 사용자는
서비스A로부터 결과를 응답 받습니다.
2.2. pom.xml
spring-cloud-starter-openfeign의존성을 추가합니다.
<properties>
<spring-cloud.version>2021.0.5</spring-cloud.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>
</dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>${spring-cloud.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
2.3. HealthClient for ServiceA
ServiceA 프로젝트에서 작업을 수행합니다.
서비스B에게 API 요청하기 위한 클라이언트를 만듭니다.- 이름과 URL을 지정합니다.
- 이름은 필수 값입니다.
- 테스트를 위해 도커 컴포즈(docker compose) 파일에 명시된 서비스 이름을 작성합니다.
- GET 요청이므로
@GetMapping애너테이션을 사용합니다.서비스B에는 요청을 받기 위한/health경로가 존재합니다.
package action.in.blog.client;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
@FeignClient(name = "health-client", url = "http://b-service:8080")
public interface HealthClient {
@GetMapping(path = "/health")
String health();
}
2.4. HealthController Class for ServiceA
ServiceA 프로젝트에서 작업을 수행합니다.
- 요청을 받을 수 있도록
/health경로 생성합니다.
package action.in.blog.controller;
import action.in.blog.client.HealthClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class HealthController {
private final HealthClient healthClient;
public HealthController(HealthClient healthClient) {
this.healthClient = healthClient;
}
@GetMapping("/health")
public String health() {
return String.format("ServiceA's Health - OK / ServiceB's Health - %s", healthClient.health());
}
}
2.5. AServiceApplication Class for ServiceA
ServiceA 프로젝트에서 작업을 수행합니다.
@FeignClient사용을 위해@EnableFeignClients애너테이션을 추가합니다.
package action.in.blog;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.openfeign.EnableFeignClients;
@EnableFeignClients
@SpringBootApplication
public class AServiceApplication {
public static void main(String[] args) {
SpringApplication.run(AServiceApplication.class, args);
}
}
2.6. HealthController Class for ServiceB
ServiceB 프로젝트에서 작업을 수행합니다.
- 요청을 받을 수 있도록
/health경로 생성합니다.
package action.in.blog.controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class HealthController {
@GetMapping("/health")
public String health() {
return "OK";
}
}
3. Test
도커 컴포즈로 테스트 환경을 구축합니다.
3.1. Dockerfile
FROM maven:3.8.6-jdk-11 as MAVEN_BUILD
WORKDIR /build
COPY pom.xml .
RUN mvn dependency:go-offline
COPY src ./src
RUN mvn package -Dmaven.test.skip=true
FROM openjdk:11-jdk-slim-buster
WORKDIR /app
ARG JAR_FILE=*.jar
COPY --from=MAVEN_BUILD /build/target/${JAR_FILE} ./app.jar
EXPOSE 8080
CMD ["java", "-jar", "app.jar"]
3.2. docker-compose.yml
version: "3.9"
services:
a-service:
build: ./a-service
ports:
- "8080:8080"
b-service:
build: ./b-service
ports:
- "8081:8080"
3.3. Run Docker Compose
$ docker-compose build
[+] Building 0.0s (0/0)
[+] Building 0.1s (1/2)
=> [internal] load build definition from Dockerfile 0.0s
[+] Building 0.2s (2/4)
=> [internal] load build definition from Dockerfile 0.0s
=> => transferring dockerfile: 32B 0.0s
=> [internal] load .dockerignore 0.0s
[+] Building 4.6s (15/15) FINISHED
=> [internal] load build definition from Dockerfile 0.0s
=> => transferring dockerfile: 32B 0.0s
=> [internal] load .dockerignore 0.0s
=> => transferring context: 2B 0.0s
=> [internal] load metadata for docker.io/library/openjdk:11-jdk-slim-buster 4.3s
=> [internal] load metadata for docker.io/library/maven:3.8.6-jdk-11 4.4s
=> [maven_build 1/6] FROM docker.io/library/maven:3.8.6-jdk-11@sha256:805f366910aea2a91ed263654d23df58bd239f218b2f9562ff51305be81fa215 0.0s
=> [stage-1 1/3] FROM docker.io/library/openjdk:11-jdk-slim-buster@sha256:863ce6f3c27a0a50b458227f23beadda1e7178cda0971fa42b50b05d9a5dcf55 0.0s
=> [internal] load build context 0.0s
=> => transferring context: 953B 0.0s
=> CACHED [stage-1 2/3] WORKDIR /app 0.0s
=> CACHED [maven_build 2/6] WORKDIR /build 0.0s
=> CACHED [maven_build 3/6] COPY pom.xml . 0.0s
=> CACHED [maven_build 4/6] RUN mvn dependency:go-offline 0.0s
[+] Building 4.7s (15/15) FINISHED
=> [internal] load build definition from Dockerfile 0.0s
=> => transferring dockerfile: 32B 0.0s
=> [internal] load .dockerignore 0.0s
=> => transferring context: 2B 0.0s
=> [internal] load metadata for docker.io/library/openjdk:11-jdk-slim-buster 4.3s
=> [internal] load metadata for docker.io/library/maven:3.8.6-jdk-11 4.4s
=> [maven_build 1/6] FROM docker.io/library/maven:3.8.6-jdk-11@sha256:805f366910aea2a91ed263654d23df58bd239f218b2f9562ff51305be81fa215 0.0s
=> [internal] load build context 0.0s
=> => transferring context: 825B 0.0s
=> [stage-1 1/3] FROM docker.io/library/openjdk:11-jdk-slim-buster@sha256:863ce6f3c27a0a50b458227f23beadda1e7178cda0971fa42b50b05d9a5dcf55 0.0s
=> CACHED [stage-1 2/3] WORKDIR /app 0.0s
=> CACHED [maven_build 2/6] WORKDIR /build 0.0s
=> CACHED [maven_build 3/6] COPY pom.xml . 0.0s
=> CACHED [maven_build 4/6] RUN mvn dependency:go-offline 0.0s
=> CACHED [maven_build 5/6] COPY src ./src 0.0s
=> CACHED [maven_build 6/6] RUN mvn package -Dmaven.test.skip=true 0.0s
=> CACHED [stage-1 3/3] COPY --from=MAVEN_BUILD /build/target/*.jar ./app.jar 0.0s
=> exporting to image 0.0s
=> => exporting layers 0.0s
=> => writing image sha256:a5a64359c420aacc54dbfced07a7ea4f7c5e46faa43e3c58e49031361466831e 0.0s
=> => naming to docker.io/library/2021-03-04-spring-cloud-openfeign-backend 0.0s
$ docker-compose up -d
[+] Running 2/2
- Container 2021-03-04-spring-cloud-openfeign-a-service-1 Started 0.8s
- Container 2021-03-04-spring-cloud-openfeign-b-service-1 Started
Test Result
사용자 터미널에서 cURL 명령어를 통해 테스트를 수행합니다.
$ curl http://localhost:8080/health
StatusCode : 200
StatusDescription :
Content : ServiceA's Health - OK / ServiceB's Health - OK
RawContent : HTTP/1.1 200
Keep-Alive: timeout=60
Connection: keep-alive
Content-Length: 47
Content-Type: text/plain;charset=UTF-8
Date: Sat, 04 Feb 2023 12:43:58 GMT
ServiceA's Health - OK / ServiceB's He...
Forms : {}
Headers : {[Keep-Alive, timeout=60], [Connection, keep-alive], [Content-Length, 47], [Content-Type, text/plain;charset=UTF-8]...}
Images : {}
InputFields : {}
Links : {}
ParsedHtml : mshtml.HTMLDocumentClass
RawContentLength : 47
CLOSING
유틸성 클래스를 만들어 HTTP 요청을 다루는 코드를 오래된 시스템에서 종종 보았습니다.
HttpURLConnection, I/O Stream 클래스를 사용해 불필요한 코드가 많았는데, FeignClient는 인터페이스와 애너테이션을 통해 비즈니스와 관련 없는 코드들을 최대한 단순화시킵니다.
spring-cloud 생태계를 조성하는 다른 컴포넌트들과 함께 사용하면 더욱 좋습니다.
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