项目地址：

github地址

服务熔断和服务降级异同

相同点：让用户体验到的是某些功能暂时不可用；都是从可用性和可靠性出发，为了防止系统崩溃；
不同点：
服务熔断：一般是某个服务(下游服务)故障引起，
服务降级：一般是从整体负荷考虑；

服务熔断的实现方式

1.在服务端添加hystrix坐标

<dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-hystrix</artifactId></dependency>

2.在对应需要熔断的接口的地方添加注解并编写熔断错误提示的代码

具体的注解是：@HystrixCommand(fallbackMethod = "processHystrix_Get"),其中的fallbackMethod是一旦服务抛出异常之后，会对该参数指定的方法进行调用返回
示例代码：

package com.debuggg.cloud.controller;import com.debuggg.cloud.entities.Dept;
import com.debuggg.cloud.service.DeptService;
import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.web.bind.annotation.*;import java.util.List;@RestController
public class DeptController {@Autowiredprivate DeptService deptService;@Autowiredprivate DiscoveryClient discoveryClient;@RequestMapping(value = "/dept/list",method = RequestMethod.GET)public List<Dept> list(){return deptService.list();}@RequestMapping(value = "/dept/get/{id}",method = RequestMethod.GET)@HystrixCommand(fallbackMethod = "processHystrix_Get")public Dept get(@PathVariable("id") Long id){Dept dept = deptService.get(id);if(dept == null){throw new RuntimeException("不能为空！");}else{return dept;}}@RequestMapping(value = "/dept/add",method = RequestMethod.POST)public Boolean add(@RequestBody Dept dept){return deptService.add(dept);}@RequestMapping(value = "/dept/discovery", method = RequestMethod.GET)public Object discovery(){List<String> list = discoveryClient.getServices();System.out.println("**********" + list);List<ServiceInstance> srvList = discoveryClient.getInstances("DEBUGGGCLOUD-DEPT");for (ServiceInstance element : srvList) {System.out.println(element.getServiceId() + "\t" + element.getHost() + "\t" + element.getPort() + "\t"+ element.getUri());}return this.discoveryClient;}public Dept processHystrix_Get(@PathVariable("id") Long id){return new Dept().setDeptno(id).setDname("该ID："+id+"没有没有对应的信息,null--@HystrixCommand").setDb_source("no this database in MySQL");}
}

服务降级的实现方式

服务降级：服务降级处理时在客户端实现完成的，与服务端没有关系

1.修改microservicecloud-api工程，根据已经有的DeptClientService接口新建一个实现了FallbackFactory接口的类DeptClientServiceFallbackFactory,千万不要忘记在类上面新增@Component注解，大坑！！！

示例代码：

package com.debuggg.cloud.service;import com.debuggg.cloud.entities.Dept;
import feign.hystrix.FallbackFactory;
import org.springframework.stereotype.Component;import java.util.List;@Component
public class DeptClientServiceFallback implements FallbackFactory<DeptClientService> {@Overridepublic DeptClientService create(Throwable throwable) {return new DeptClientService() {@Overridepublic Dept get(long id) {return new Dept().setDeptno(id).setDname("该ID："+id+"没有没有对应的信息,Consumer客户端提供的降级信息,此刻服务Provider已经关闭").setDb_source("no this database in MySQL");}@Overridepublic List<Dept> list() {return null;}@Overridepublic boolean add(Dept dept) {return false;}};}
}

2.修改microservicecloud-api工程，DeptClientService接口在注解@FeignClient中添加fallbackFactory属性值

@FeignClient(value = "DEBUGGGCLOUD-DEPT",fallbackFactory = DeptClientServiceFallback.class)

3.修改yml

server:port: 10001
eureka:client:service-url:defaultZone: http://eureka7001.com:7001/eureka/,http://eureka7002.com:7002/eureka/,http://eureka7003.com:7003/eureka/register-with-eureka: false
**
feign:hystrix:enabled: true #启用服务降级**