Feign 是一個宣告web服務客戶端，這便得編寫web服務客戶端更容易，使用Feign 建立一個介面並對它進行註解，它具有可插拔的註解支援包括Feign註解與JAX-RS註解，Feign還支援可插拔的編碼器與解碼器，Spring Cloud 增加了對 Spring MVC的註解，Spring Web 預設使用了HttpMessageConverters, Spring Cloud 整合 Ribbon 和 Eureka 提供的負載均衡的HTTP客戶端 Feign.

1.建立Spring Cloud maven專案，新增pom引用如下：

<?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>1.4.0.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.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-feign</artifactId>
        </dependency>
        <dependency>
        	<groupId>org.springframework.boot</groupId>
        	<artifactId>spring-boot-starter-web</artifactId>
 		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
	</dependencies>
	
	<dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Dalston.SR1</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

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

2.application.properties配置如下：

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

3.Application啟動檔案新增@EnableDiscoveryClient和@EnableFeignClients註解。

package com.example.servicefeign;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.feign.EnableFeignClients;

@EnableDiscoveryClient
@SpringBootApplication
@EnableFeignClients
public class ServiceFeignApplication {

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

4.建立服務介面類HelloService。@FeignClient的value值為服務提供者的服務註冊名。

import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@FeignClient(value = "COMPUTE-SERVICE")
public interface  HelloService {
    @RequestMapping(value = "/hello",method = RequestMethod.GET)
    String sayHiFromClientOne();
}
 

5.在Colntroller呼叫介面。

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import com.example.servicefeign.service.HelloService;

@RestController
public class HelloController {
	 	@Autowired
	    HelloService helloService;
	    @RequestMapping(value = "/hello")
	    public String hi(){
	        return helloService.sayHiFromClientOne();
	    }
}

執行EUREKA，服務提供者，及本Feign消費服務。

訪問service-feign的controller方法：