Dubbo服务容错（整合hystrix）

简介：Hystrix旨在通过控制那些访问远程系统、服务和第三方库的节点从而对延迟和故障提供更强大的容错能力，Hystrix具备拥有回退机制和断路器功能的线程和信号隔离、请求缓存和请求打包以及监控和配置等功能。

1）、在pom文件中导入依赖（服务提供者和服务消费者都需要导入）

         <dependency>
             <groupId>org.springframework.cloud</groupId>
             <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
             <version>1.4.4.RELEASE</version>
         </dependency>

2）、在主程序启动类上添加@EnableHystrix注解开启服务容错（服务提供者和服务消费者都需要添加）

 package cn.coreqi;

 import com.alibaba.dubbo.config.spring.context.annotation.EnableDubbo;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.cloud.netflix.hystrix.EnableHystrix;

 @SpringBootApplication
 @EnableDubbo
 @EnableHystrix  //开启服务容错
 public class SpringbootdubboserviceproviderApplication {

     public static void main(String[] args) {
         SpringApplication.run(SpringbootdubboserviceproviderApplication.class, args);
     }

 }

3）、在服务提供者实现类中方法上添加@HystrixCommand注解

 package cn.coreqi.service.impl;

 import cn.coreqi.entities.User;
 import cn.coreqi.service.UserService;
 import com.alibaba.dubbo.config.annotation.Service;
 import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
 import org.springframework.stereotype.Component;

 import java.util.ArrayList;
 import java.util.List;

 @Component  //org.springframework.stereotype.Component
 @Service    //com.alibaba.dubbo.config.annotation.Service
 public class UserServiceImpl implements UserService {

     private static List<User> users = new ArrayList<>();

     static {
         users.add(new User(1,"fanqi","123456",1));
         users.add(new User(2,"zhangsan","123456",1));
         users.add(new User(3,"lisi","123456",1));
         users.add(new User(4,"wangwu","123456",1));
     }

     @HystrixCommand
     @Override
     public void addUser(User user) {
         users.add(user);
     }

     @HystrixCommand
     @Override
     public void delById(Integer id) {
         for (User s:users){
             if(s.getId() == id){
                 users.remove(s);
                 break;
             }
         }
     }

     @HystrixCommand
     @Override
     public void modifyUser(User user) {
         delById(user.getId());
         addUser(user);
     }

     @HystrixCommand
     @Override
     public User getById(Integer id) {
         for (User s:users){
             if(s.getId() == id){
                 return s;
             }
         }
         return null;
     }

     @HystrixCommand
     @Override
     public List<User> getList() {
         return users;
     }
 }

4）、在服务消费者调用服务提供者的方法上添加@HystrixCommand注解并指定fallbackMethod属性，重写fallbackMethod指定的方法。

 package cn.coreqi.controller;

 import cn.coreqi.entities.User;
 import cn.coreqi.service.UserService;
 import com.alibaba.dubbo.config.annotation.Reference;
 import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
 import org.springframework.stereotype.Controller;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.ResponseBody;

 import java.util.List;

 @Controller
 public class UserController {

     @Reference()
     private UserService userService;

     @HystrixCommand(fallbackMethod = "test1")
     @ResponseBody
     @RequestMapping("/users")
     public List<User> getUsers(){
         return userService.getList();
     }

     public List<User> test1(){
         return null;
     }
 }