Spring Cloud声明式调用Feign负载均衡客户端

Fegin是什么？

Feign 是一个声明式的伪 Http 客户端，它使得写 Http 客户端变得更简单。使用 Feign，只需要创建一个接口并注解。它具有可插拔的注解特性，可使用 Feign 注解和 JAX-RS 注解。Feign 支持可插拔的编码器和解码器。Feign 默认集成了 Ribbon，Nacos 也很好的兼容了 Feign，默认实现了负载均衡的效果

• Feign 采用的是基于接口的注解
• Feign 整合了 Ribbon

创建Fegin服务消费者工程

创建一个工程名为 spring-cloud-alibaba-nacos-consumer-feign 的服务消费者项目，pom.xml 配置如下：

<?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>

    <parent>
        <groupId>com.dsy</groupId>
        <artifactId>spring-cloud-alibaba-dependencies</artifactId>
        <version>1.0.0-SNAPSHOT</version>
        <relativePath>../spring-cloud-alibaba-dependencies/pom.xml</relativePath>
    </parent>

    <artifactId>spring-cloud-alibaba-nacos-consumer-feign</artifactId>
    <packaging>jar</packaging>

    <name>spring-cloud-alibaba-nacos-consumer-feign</name>
    <inceptionYear>2019-Now</inceptionYear>

    <dependencies>
        <!-- Spring Boot Begin -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <!-- Spring Boot End -->

        <!-- Spring Cloud Begin -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
        <!-- Spring Cloud End -->
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <mainClass>com.dsy.spring.cloud.alibaba.nacos.consumer.feign.NacosConsumerFeignApplication</mainClass>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

创建应用主类

package com.dsy.spring.cloud.alibaba.nacos.consumer.feign;

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

/**
 * @author sanya deng
 * @version 1.0.0
 * @Title: NacosConsumerFeignApplication
 * @ProjectName SpringCloud
 * @Description: 服务消费者
 * @email forestsancy@163.com
 * @date 2019-04-12 16:29
 */
@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
//通过 @EnableFeignClients 注解开启 Feign 功能
public class NacosConsumerFeignApplication {
    public static void main(String[] args) {
        SpringApplication.run(NacosConsumerFeignApplication.class, args);
    }
}

创建Feign 接口

package com.dsy.spring.cloud.alibaba.nacos.consumer.feign.service;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;

/**
 * @author sanya deng
 * @version 1.0.0
 * @Title: EchoService
 * @ProjectName SpringCloud
 * @Description: TODO
 * @email forestsancy@163.com
 * @date 2019-04-12 16:31
 */
//通过 @FeignClient("服务名") 注解来指定调用哪个服务
@FeignClient(value = "nacos-provider")
public interface EchoService {

    @GetMapping(value = "/echo/{message}")
    String echo(@PathVariable("message") String message);

}

创建Controller并实现一个HTTP接口

package com.dsy.spring.cloud.alibaba.nacos.consumer.feign.controller;

import com.dsy.spring.cloud.alibaba.nacos.consumer.feign.service.EchoService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

/**
 * @author sanya deng
 * @version 1.0.0
 * @Title: NacosConsumerFeignController
 * @ProjectName SpringCloud
 * @Description: TODO
 * @email forestsancy@163.com
 * @date 2019-04-12 16:32
 */

@RestController
public class NacosConsumerFeignController {

    @Autowired
    private EchoService echoService;

    @GetMapping(value = "/echo/hi")
    public String echo() {
        return echoService.echo("Hi Feign");
    }
}

application.yml

spring:
  application:
    name: nacos-consumer-feign
  cloud:
    nacos:
      discovery:
        server-addr: 127.0.0.1:8848

server:
  port: 9093

management:
  endpoints:
    web:
      exposure:
        include: "*"

启动工程

通过浏览器访问 http://localhost:8848/nacos，即 Nacos Server 网址

图片.png
可以发现多了一个名为 nacos-consumer-feign 的服务

测试负载均衡

启动多个 consumer-provider 实例，效果图如下：

图片.png
通过curl多次访问 http://localhost:9092/echo/hi , 在终端交替显示： 图片.png