springboot整合feign实现RPC调用，并通过Hystrix实现降级-编程知识

一、服务提供者

二、服务消费者

三、测试效果

四、开启Hystrix实现降级功能

feign/openfeign和dubbo是常用的微服务RPC框架，由于feigin内部已经集成ribbon，自带了负载均衡的功能，当有多个同名的服务注册到注册中心时，会根据ribbon默认的负载均衡算法将请求分配到不同的服务。这篇文章就简单介绍一下怎么使用feign来调用远程的服务。

首先，需要有一个微服务注册中心来提供服务注册与发现，本章就使用之前创建的eureka作为注册中心。点击以下文章链接，教你快速搭建一个eureka server

springboot整合eureka、config搭建注册中心和配置中心https://blog.csdn.net/heyl163_/article/details/131715281首先，要实现服务间的调用，需要有服务提供者和服务消费者，创建两个项目，分别用于服务提供者和服务消费者。

一、服务提供者

创建一个springboot项目，取名为provider

1、修改maven配置文件pom.xml

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.3.4.RELEASE</version><relativePath/></parent><groupId>com.example</groupId><artifactId>provider</artifactId><version>0.0.1-SNAPSHOT</version><properties><java.version>1.8</java.version><eureka.version>1.4.4.RELEASE</eureka.version></properties><dependencyManagement><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-dependencies</artifactId><version>Hoxton.SR12</version><type>pom</type><scope>import</scope></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-eureka-server</artifactId><version>${eureka.version}</version></dependency></dependencies></dependencyManagement><dependencies><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><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-eureka-server</artifactId></dependency></dependencies><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin></plugins></build>
</project>

2、修改系统配置文件

server:port: 8085spring:application:name: providereureka:instance:hostname: localhostclient:service-url:defaultZone: http://${eureka.instance.hostname}:8761/eureka

3、创建一个controller

在根目录下创建controller包，然后在controller包下创建一个UserController

package com.example.provider.controller;import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;/*** @author heyunlin* @version 1.0*/
@RestController
@RequestMapping(path = "/user", produces = "application/json;charset=utf-8")
public class UserController {@RequestMapping(value = "/name", method = RequestMethod.GET)public String name() {return "heyunlin";}}

4、启动类上添加@EnableDiscoveryClient注解

package com.example.provider;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;@EnableDiscoveryClient
@SpringBootApplication
public class ProviderApplication {public static void main(String[] args) {SpringApplication.run(ProviderApplication.class, args);}}

二、服务消费者

1、创建一个springboot项目并命名为consumer

2、修改pom.xml配置文件

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.3.4.RELEASE</version><relativePath/></parent><groupId>com.example</groupId><artifactId>consumer</artifactId><version>0.0.1-SNAPSHOT</version><properties><java.version>1.8</java.version><eureka.version>1.4.4.RELEASE</eureka.version></properties><dependencyManagement><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-dependencies</artifactId><version>Hoxton.SR12</version><type>pom</type><scope>import</scope></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-eureka-server</artifactId><version>${eureka.version}</version></dependency></dependencies></dependencyManagement><dependencies><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><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-eureka-server</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-openfeign</artifactId></dependency></dependencies>
</project>

3、修改配置文件，注册到eureka

server:port: 8086spring:application:name: consumereureka:instance:hostname: localhostclient:service-url:defaultZone: http://${eureka.instance.hostname}:8761/eureka

4、通过feign调用远程的方法

根目录下创建feign包，在feign包下创建一个接口FeignService（类名不重要）

@FeignClient("provider")指定注册到eurka的服务名

@RequestMapping的路径写provider服务的控制器接口路径

package com.example.consumer.feign;import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;/*** @author heyunlin* @version 1.0*/
@FeignClient("provider")
public interface FeignService {@RequestMapping(value = "/user/name", method = RequestMethod.GET)String name();}

5、最后，创建一个控制器类，类名随便取

package com.example.consumer.controller;import com.example.consumer.feign.FeignService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;/*** @author heyunlin* @version 1.0*/
@RestController
@RequestMapping("/user")
public class UserController {@AutowiredFeignService feignService;@RequestMapping(value = "/name", method = RequestMethod.GET)public String name() {return feignService.name();}}

这时候@Autowired会报错，找不到FeignService的bean，因为没有在配置类上面添加@EnableFeignClients注解

package com.example.consumer;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;@EnableFeignClients
@EnableDiscoveryClient
@SpringBootApplication
public class ConsumerApplication {public static void main(String[] args) {SpringApplication.run(ConsumerApplication.class, args);}}

三、测试效果

完成以上操作之后，依次启动euraka-server，provider和consumer

浏览器上访问consumer的控制器地址http://localhost:8086/user/name，发现成功返回了字符串。

四、开启Hystrix实现降级功能

首先需要开启hystrix

在pom.xml文件中添加配置

feign:hystrix:enabled: true

然后创建一个FeignService的实现类，交给spring管理

package com.example.consumer.feign;import org.springframework.stereotype.Component;/*** @author heyunlin* @version 1.0*/
@Component
public class FeignServiceImpl implements FeignService {@Overridepublic String name() {return "error";}}

最后，在FeiginService的@FeiginCilent上指定fallback=FeignServiceImpl.class

@FeignClient(value = "provider", fallback = FeignServiceImpl.class)

完成以上配置之后，重启consumer，访问http://localhost:8086/user/name时正确调用了provider的控制器方法，得到了正确的结果。

接着把关掉provider项目，再访问，发现调用失败，成功执行了配置的降级方法，直接返回了error

好了，springboot整合feign的介绍到这里就完了，代码已开源，按需获取~

注册中心

eurekahttps://gitee.com/he-yunlin/eureka.git服务提供者

providerhttps://gitee.com/he-yunlin/provider.git服务消费者

consumerhttps://gitee.com/he-yunlin/consumer.git