一、Feign簡介
Feign是收到了 Retrofit, JAXRS-2.0, and WebSocket啟發而產生的http客戶端。極大的簡化了restful風格的http API引數繫結。Feign預設集成了Ribbon，使用Feign可以指定編碼解碼，重請求等功能，需要進行配置
二、Feign的使用
1、建立專案consulclient4，引入依賴

<dependencyManagement>
        <dependencies>
            <dependency>
                <groupId
 
>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>2.0.0.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
 


            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Finchley.M8</version>
                <type>pom</type>
                <scope
 
>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <!--用於監控與管理-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-actuator</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-config</artifactId>
        </dependency>

        <!--config server-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-config-server</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-consul</artifactId>
        </dependency>

        <!--服務發現依賴-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-consul-discovery</artifactId>
        </dependency>

        <!--用於consul配置-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-consul-config</artifactId>
        </dependency>

        <!--Feign的依賴-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>

    </dependencies>

2、建立Feign介面

@FeignClient("consulservice3")//依然用我們的使用過的service consulservice3
public interface SayService {

    @RequestMapping(value = "say")
    String say();
}

3、使用Feign

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients//必不可少，使用此註解才能掃描到Feign介面，負責不會注入SayService
@RestController
public class ConsulClient4App {

    @Autowired
    private SayService sayService;

    @RequestMapping("say")
    public String say(){
        return sayService.say();
    }

    public static void main(String[] args){
        SpringApplication.run(ConsulClient4App.class, args);
    }
}

4、以埠9999啟動ConsulClient4App，呼叫介面localhost:9999/say

原始碼：
https://github.com/NapWells/spring_cloud_learn/tree/master/discover_server_with_consul/springcloudlearn/consulclient4