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;
    }
}