新建一個spring-boot工程，取名為serice-feign，在它的pom檔案引入Feign的起步依賴spring-cloud-starter-feign、Eureka的起步依賴spring-cloud-starter-netflix-eureka-client、Web的起步依賴spring-boot-starter-web，程式碼如下：

pom檔案如下：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example</groupId>
    <artifactId>service-feign</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>service-feign</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.1.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
            <version>2.0.1.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
            <version>2.0.1.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
            <version>2.0.1.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

在工程的配置檔案application.yml檔案，指定程式名為service-feign，埠號為8765，服務註冊地址為http://localhost:8761/eureka/ ，程式碼如下：

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/
server:
  port: 8765
spring:
  application:
    name: service-feign

在程式的啟動類ServiceFeignApplication ，加上@EnableFeignClients註解開啟Feign的功能：

@SpringBootApplication
@EnableEurekaClient
@EnableDiscoveryClient
@EnableFeignClients
public class ServiceFeignApplication {

    public static void main(String[] args) {
        SpringApplication.run( ServiceFeignApplication.class, args );
    }
}

定義一個feign介面，通過@ FeignClient（“服務名”），來指定呼叫哪個服務。比如在程式碼中呼叫了service-hi服務的“/hi”介面，程式碼如下：

@FeignClient(value = "service-hi")
public interface SchedualServiceHi {
    @RequestMapping(value = "/hi",method = RequestMethod.GET)
    String sayHiFromClientOne(@RequestParam(value = "name") String name);
}

在Web層的controller層，對外暴露一個”/hi”的API介面，通過上面定義的Feign客戶端SchedualServiceHi 來消費服務。程式碼如下：

@RestController
public class HiController {


    //編譯器報錯，無視。 因為這個Bean是在程式啟動的時候注入的，編譯器感知不到，所以報錯。
    @Autowired
    SchedualServiceHi schedualServiceHi;

    @GetMapping(value = "/hi")
    public String sayHi(@RequestParam String name) {
        return schedualServiceHi.sayHiFromClientOne( name );
    }
}

啟動程式，多次訪問http://localhost:8765/hi?name=forezp,瀏覽器交替顯示：

hi forezp,i am from port:8762

hi forezp,i am from port:8763