引入依赖
 

<!--spring-cloud-hystrix 服务保护-->
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-hystrix</artifactId>
		</dependency>

启动类上面添加注解

@EnableCircuitBreaker

package com.hx.order;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients(basePackages="com.hx.order.client")
@EnableCircuitBreaker
public class OrderApplication {

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

}

其实也可以用@SpringCloudApplication来代替上面的三个注解：

package com.hx.order;

import org.springframework.boot.SpringApplication;
import org.springframework.cloud.client.SpringCloudApplication;
import org.springframework.cloud.openfeign.EnableFeignClients;

@EnableFeignClients(basePackages="com.hx.order.client")
@SpringCloudApplication
public class OrderApplication {

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

}

@SpringCloudApplication源码（已经包含了这三个注解）

1. 服务降级

   package com.hx.order.controller;
   
   import com.netflix.hystrix.contrib.javanica.annotation.DefaultProperties;
   import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
   import com.netflix.hystrix.contrib.javanica.annotation.HystrixProperty;
   import org.springframework.web.bind.annotation.GetMapping;
   import org.springframework.web.bind.annotation.RestController;
   import org.springframework.web.client.RestTemplate;
   
   import java.util.Arrays;
   
   /**
    * 服务管理----熔断限流降级
    */
   @RestController
   @DefaultProperties(defaultFallback = "defaultFallback")
   public class HystrixController {
   
   
       /**
        * RestTemplate  发起的http请求
        * 降级就是捕捉异常（自定义可以抛出异常，就会降级）
        * 超时时间设置为3秒
        * @return
        */
       @HystrixCommand(commandProperties = {
               @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds",value = "3000")
       })
       @GetMapping("/getProductInfoList")
       public String getProductInfoList() {
           RestTemplate restTemplate = new RestTemplate();
           return restTemplate.postForObject("http://127.0.0.1:8052/product/listForOrder",
                   Arrays.asList("123"),
                   String.class);
       }
   
       @HystrixCommand
       @GetMapping("/get")
       public String get() {
           throw new RuntimeException("error");
       }
   
       @HystrixCommand(fallbackMethod = "fallback")
       @GetMapping("/query")
       public String query() {
           throw new RuntimeException("error");
       }
   
       private String fallback() {
           return "太拥挤了，请稍后再试~~";
       }
   
       private String defaultFallback() {
           return "默认提示：太拥挤了，请稍后再试~~";
       }
   }
   

   1.@HystrixCommand(fallbackMethod = "fallback") 有属性fallbackMethod的时候就会查找定义的失败方法进行降级。
   2.如果没有，也就是直接加@HystrixCommand，注解就需要再在类的上面添加@DefaultProperties(defaultFallback = "defaultFallback")
   3.超时设置：3秒
   ，如果在调用的接口上面添加线程阻塞2秒，就会调用失败，因为Hystrix默认调用时间时1秒。

   @HystrixCommand(commandProperties = {
           @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds",value = "3000")
   })

    

2. 依赖隔离

   @HystrixCommand(commandProperties = {
               @HystrixProperty(name = "circuitBreaker.enabled",value = "true"),
               @HystrixProperty(name = "circuitBreaker.requestVolumeThreshold",value = "10"),
               @HystrixProperty(name = "circuitBreaker.sleepWindowInMilliseconds",value = "10000"),
               @HystrixProperty(name = "circuitBreaker.errorThresholdPercentage",value = "60")
       })

   circuitBreaker.enabled=true     开启熔断器
   circuitBreaker.requestVolumeThreshold=10  请求量保留10
   circuitBreaker.sleepWindowInMilliseconds=10000   休眠10s
   circuitBreaker.errorThresholdPercentage=60   错误阈值百分比=60
   

3. 使用配置
    

   spring:
     application:
       name: order
     cloud:
       config:
         discovery:
           enabled: true
           service-id: CONFIG
         profile: dev
   eureka:
     client:
       service-url:
         defaultZone: http://localhost:8761/eureka/
   hystrix:
     command:
       default:
         execution:
           isolation:
             thread:
               timeoutInMilliseconds: 1000
       getProductInfoList: # commandKey = 单独配置的方法名称
         execution:
           isolation:
             thread:
               timeoutInMilliseconds: 3000
   feign:
     hystrix:
       enabled: true

   

4. feign-hystrix的使用
   1.因为feign内置了hystrix，所有直接配置就可以。
   
   

   feign:
     hystrix:
       enabled: true

   
   2.然后在@FeignClient注解添加属性 fallbac=xxx.class,自定义这个类现在这个接口，在接口上添加spring注解@Component，再在实现的方法里面实现你处理错误的逻辑。
   
   这里是内部类案例 -ProductClientFallback 

   package com.hx.order.client;
   
   import com.hx.order.dataobject.ProductInfo;
   import com.hx.order.dto.CartDTO;
   import org.springframework.cloud.openfeign.FeignClient;
   import org.springframework.stereotype.Component;
   import org.springframework.web.bind.annotation.GetMapping;
   import org.springframework.web.bind.annotation.PostMapping;
   import org.springframework.web.bind.annotation.RequestBody;
   
   import java.util.List;
   import java.util.Map;
   
   @FeignClient(name = "product",fallback =ProductClient.ProductClientFallback.class)  //添加此注解说明是服务调用  name是服务的名称
   public interface ProductClient {
   
       @PostMapping("/product/listForOrder")
           //用来识别调用的接口
       List<ProductInfo> listForOrder(@RequestBody List<String> productIdList);
   
       @PostMapping("/product/decreseStock")
       Boolean decreseStock(@RequestBody List<CartDTO> cartDTOList);
   
       /**内部类
        *
        */
       @Component
       static class ProductClientFallback implements ProductClient{
   
           @Override
           public List<ProductInfo> listForOrder(List<String> productIdList) {
               return null;
           }
   
           @Override
           public Boolean decreseStock(List<CartDTO> cartDTOList) {
               return false;
           }
       }
   }
   

   
   3.如果你当前服务是依赖的是别的服务，需要在你的启动类上添加包扫描的注解：
   @ComponentScan(basePackages = "com") //此注解的作用就是把包扫描的范围扩大到com,也就可以把依赖过来的包也扫描上，如果就是当前服务就不需要添加。

   package com.hx.order;
   
   import org.springframework.boot.SpringApplication;
   import org.springframework.cloud.client.SpringCloudApplication;
   import org.springframework.cloud.openfeign.EnableFeignClients;
   import org.springframework.context.annotation.ComponentScan;
   
   @EnableFeignClients(basePackages="com.hx.order.client")
   @SpringCloudApplication
   @ComponentScan(basePackages = "com") //此注解的作用就是把包扫描的范围扩大到com,也就可以把依赖过来的包也扫描上
   public class OrderApplication {
   
       public static void main(String[] args) {
           SpringApplication.run(OrderApplication.class, args);
       }
   
   }
   

    

5. hystrix-dashboard  仪表板
   添加依赖

   <!--spring-cloud-hystrix-dashboard  服务熔断看板-->
   	   <dependency>
   			<groupId>org.springframework.cloud</groupId>
   			<artifactId>spring-cloud-starter-hystrix-dashboard</artifactId>
               <version>1.4.7.RELEASE</version>
   		</dependency>
   
   <dependency>
   			<groupId>org.springframework.boot</groupId>
   			<artifactId>spring-boot-starter-actuator</artifactId>
   		</dependency>

   如果引入过spring-cloud-starter-stream-rabbit，这个，下面的actuator就可以不需要引入了，因为stream里面引入过这个组件。
   启动类上面添加注解

   @EnableHystrixDashboard
   如果添加失败，再添加依赖
   
   

   <!--由于是spring boot 2.0.X版本问题-->
   		<dependency>
   			<groupId>org.springframework.cloud</groupId>
   			<artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
   		</dependency>

   因为用的是boot2.0所有添加配置文件
    

   management:
     endpoints:
       web:
         exposure:
           include: ["health","info","hystrix.stream"]

   启动服务访问localhost:port[你的端口号]/hystrix
   
   
   上面的0代表什么意思呢，就和页面上面的，颜色是一一对应的。