SpringCloud -- Feign & Hystrix 介绍

这两个组件的作用是解决多个微服务之间的调用，一个是解决如何调用，一个解决调用时出现了错误怎么解决

在之前多个服务进行调用可以直接使用http请求或者rest 请求去请求每一个微服务

 Feign 时依赖于Ribbon可以使用appname 转 ip：port，Fegin是对 Ribbon的再次封装，使得微服务之间的调用更简单

 创建一个 有Fegin和Hystrix的项目

pom.xml 文件

        
        
            org.springframework.boot
            spring-boot-starter-web
        
        
        
            org.springframework.cloud
            spring-cloud-starter-netflix-eureka-client
        
        
        
            org.springframework.cloud
            spring-cloud-starter-openfeign
        
        
        
            org.springframework.cloud
            spring-cloud-starter-netflix-hystrix
        
        
        
            org.springframework.boot
            spring-boot-starter-data-jpa
        
        
        
            mysql
            mysql-connector-java
            5.1.47
            runtime
        
        
        
            com.imooc.homepage
            homepage-common
            1.0-SNAPSHOT
        
    

    
    
        
            
                org.springframework.boot
                spring-boot-maven-plugin
            
        
    

启动类的配置

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.data.jpa.repository.config.EnableJpaAuditing;

@EnableJpaAuditing
@EnableFeignClients
@EnableCircuitBreaker
@EnableEurekaClient
@SpringBootApplication
public class HomepageUserApplication {
    public static void main(String[] args) {
        SpringApplication.run(HomepageUserApplication.class,args);
    }
}

配置文件的配置application.yml

server:
  port: 7000
  servlet:
    context-path: /homepage-user

spring:
  main:
    allow-bean-definition-overriding: true
  application:
    name: eureka-client-homepage-user
  jpa:
    show-sql: true
    hibernate:
      ddl-auto: none
    properties:
      hibernate.format_sql: true
    open-in-view: false
  datasource:
    url: jdbc:mysql://127.0.0.1:3306/imooc_homepage_sc?autoReconnect=true&useUnicode=true&characterEncoding=utf8&useSSL=false
    username: root
    password: 123456
    driver-class-name: com.mysql.jdbc.Driver
    tomcat:
      max-active: 4
      min-idle: 2
      initial-size: 2

eureka:
  client:
    service-url:
      defaultZone: http://server1:8000/eureka/

feign:
  hystrix:
    enabled: true

为服务的目录结构

Feign接口的定义

import com.imooc.homepage.CourseInfo;
import com.imooc.homepage.CourseInfosRequest;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

import java.util.List;

/**
 * 通过 feign 访问 其他的微服务
 * 用户微服务访问 课程微服务
 */
@FeignClient(value = "eureka-client-homepage-course",
                fallback = CourseClientHystrix.class)
public interface CourseClient {

    @RequestMapping(value = "/homepage-course/get/course",
            method = RequestMethod.GET)
    CourseInfo getCourseInfo(Long id);

    @RequestMapping(value = "/homepage-course/get/courses",
            method = RequestMethod.POST)
    List getCourseInfos(@RequestBody CourseInfosRequest request);
}

熔断策略类的编写要和Fegin接口定义的方法名称要一样，所以去实现其接口

import com.imooc.homepage.CourseInfo;
import com.imooc.homepage.CourseInfosRequest;
import org.springframework.stereotype.Component;

import java.util.Collections;
import java.util.List;

/**
 * 熔断降级策略
 */
@Component
public class CourseClientHystrix implements CourseClient{
    @Override
    public CourseInfo getCourseInfo(Long id) {
        return CourseInfo.invalid();
    }

    @Override
    public List getCourseInfos(CourseInfosRequest request) {
        return Collections.emptyList();
    }
}