Spring Cloud 學習紀要二：Feign

Spring Cloud Feign：服務通信

  Spring Cloud Feign是簡化Java HTTP客戶端開發的工具，它的靈感來自於Retrofit、JAXRS-2.0和WebSocket。接下來將展示一個入門Demo。

開發環境	版本
IDEA	2018.2.6
JDK	1.8
Spring Boot	2.1.0
Spring Cloud	Greenwich.M1

新建項目

  在IDEA中通過Spring Initializr創建項目，選擇Spring Boot 2.1.0版本、選擇Maven依賴Web、Eureka Discovery(Cloud Discovery中)和Feign(Cloud Routing中)。

<dependencies>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-openfeign</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
</dependencies>

加入註解

  在入口類添加@EnableEurekaClient和@EnableFeignClients註解。

@SpringBootApplication
@EnableEurekaClient
@EnableFeignClients
public class FeignConsumerApplication {
    public static void main(String[] args) {
        SpringApplication.run(FeignConsumerApplication.class, args);
    }
}

添加配置

  在文件application.yml添加配置。

eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka/
  instance:
    prefer-ip-address: true
    instance-id: ${spring.cloud.client.ip-address}:${server.port}
    #    hostname: ConsumerName

spring:
  application:
    name: consumer

編寫接口

  在上一篇的provider項目中，新建簡單的Controller，代碼如下，運行provider項目，訪問http://localhost:8081/hello/chung可得到Hello Chung By Provider。

@RestController
@RequestMapping("/hello")
public class HelloController {
    @GetMapping("/chung")
    public String helloChung(){
        return "Hello Chung By Provider";
    }
}

  在本篇的新項目consumer中新建接口和Controller，代碼如下：

@FeignClient(name = "provider")
public interface ProviderClient {
    @RequestMapping(value = "/hello/chung")
    String hello();
}

@RestController
@RequestMapping("hello")
public class HelloController {
    @Autowired
    private ProviderClient providerClient;

    @GetMapping("/consumer")
    public String hello(){
        return providerClient.hello();
    }
}

運行項目

  在VM options設置-DServer.port=8091，運行consumer項目，可以在Eureka頁面看到本項目註冊成功，訪問http://localhost:8091/hello/consumer同樣可以得到Hello Chung By Provider，證明服務間通信正常。