前言：

在上一节里，我们学习了ribbon的使用。

我们了解到ribbon是一个客户端负载均衡机制。

而我们今天要讲的Feign呢，也是一款客户端负载均衡机制。

或者这样说，Feign封装了ribbon的负载均衡，实现了面向接口调用服务编程取缔面向服务编程。

ribbon面向服务编程：

@GetMapping("/hello")

public List<String> sayHello() {

    List<String> list = new ArrayList<>();

    for(int i=0;i<30;i++) {

        list.add(restTemplate.getForObject("http://CL-HELLO-PRODUCER/hello", String.class));

    }

    return list;

}

feign面向接口编程：

@FeignClient(value="CL-HELLO-PRODUCER")

public interface HelloService {

	@GetMapping("/hello")

	public String sayHello();

}

新建一个服务消费者（cl_hello_consumer_feign）：

1.添加依赖

<?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.xm.cloud</groupId>

	<artifactId>cl_hello_consumer_feign</artifactId>

	<version>0.0.1-SNAPSHOT</version>

	<packaging>jar</packaging>

	<name>cl_hello_consumer_feign</name>

	<description>This is a Web about springcloud</description>

	<parent>

		<groupId>org.springframework.boot</groupId>

		<artifactId>spring-boot-starter-parent</artifactId>

		<version>2.0.6.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>

		<spring-cloud.version>Finchley.SR2</spring-cloud.version>

	</properties>

	<dependencies>

		<dependency>

			<groupId>org.springframework.boot</groupId>

			<artifactId>spring-boot-starter-web</artifactId>

		</dependency>

		<dependency>

			<groupId>org.springframework.cloud</groupId>

			<artifactId>spring-cloud-starter-netflix-eureka-client</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>

	<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>

	<build>

		<plugins>

			<plugin>

				<groupId>org.springframework.boot</groupId>

				<artifactId>spring-boot-maven-plugin</artifactId>

			</plugin>

		</plugins>

	</build>

</project>

2.修改配置

eureka.client.service-url.defaultZone=http://127.0.0.1:7001/eureka/

eureka.client.register-with-eureka=false

3.开启注解

package com.xm.cloud;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.cloud.client.discovery.EnableDiscoveryClient;

import org.springframework.cloud.openfeign.EnableFeignClients;

import org.springframework.context.annotation.ComponentScan;

@EnableFeignClients

@EnableDiscoveryClient

@SpringBootApplication

public class ClHelloConsumerFeignApplication {

	public static void main(String[] args) {

		SpringApplication.run(ClHelloConsumerFeignApplication.class, args);

	}

}

4.添加Service

package com.xm.cloud.service;

import org.springframework.cloud.openfeign.FeignClient;

import org.springframework.web.bind.annotation.GetMapping;

@FeignClient(value="CL-HELLO-PRODUCER")

public interface HelloService {

	@GetMapping("/hello")

	public String sayHello();

}

5.添加Controller

package com.xm.cloud.controller;

import java.util.ArrayList;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.web.bind.annotation.GetMapping;

import org.springframework.web.bind.annotation.RestController;

import com.xm.cloud.service.HelloService;

@RestController

public class HelloController {

	@Autowired

	private HelloService helloService;

	@GetMapping("/hello")

	public List<String> sayHello() {

		List<String> list = new ArrayList<String>();

		for(int i=0;i<10;i++) {

			list.add(helloService.sayHello());

		}

		return list;

	}

}

6.测试

访问：localhost:8080/helo

0	"Hello Spring Cloud! 001号机器"
1	"Hello Spring Cloud! 003号机器"
2	"Hello Spring Cloud! 002号机器"
3	"Hello Spring Cloud! 001号机器"
4	"Hello Spring Cloud! 003号机器"
5	"Hello Spring Cloud! 002号机器"
6	"Hello Spring Cloud! 001号机器"
7	"Hello Spring Cloud! 003号机器"
8	"Hello Spring Cloud! 002号机器"
9	"Hello Spring Cloud! 001号机器"

4.Spring Cloud初相识--------Feign负载均衡的相关教程结束。