springboot整合feign实现RPC调用，并通过Hystrix实现降级

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 复制代码

<?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

XML 复制代码

server:
  port: 8085

spring:
  application:
    name: provider

eureka:
  instance:
    hostname: localhost
  client:
    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

java 复制代码

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

java 复制代码

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 复制代码

<?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

XML 复制代码

server:
  port: 8086

spring:
  application:
    name: consumer

eureka:
  instance:
    hostname: localhost
  client:
    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

java 复制代码

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

java 复制代码

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 {
    @Autowired
    FeignService 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

java 复制代码

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

XML 复制代码

feign:
  hystrix:
    enabled: true

然后创建一个FeignService的实现类，交给spring管理

java 复制代码

package com.example.consumer.feign;

import org.springframework.stereotype.Component;

/**
 * @author heyunlin
 * @version 1.0
 */
@Component
public class FeignServiceImpl implements FeignService {

    @Override
    public String name() {
        return "error";
    }

}

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

java 复制代码

@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