Spring Cloud(Dalston.SR5)--Hystrix 断路器

Spring Cloud 对 Hystrix 进行了封装，使用 Hystrix 是通过 @HystrixCommand 注解来使用的，被 @HystrixCommand 注解标注的方法，会使用 AspectJ 对其进行代理，Spring 会将相关的类转换为 Bean 放到容器中，在 @HystrixCommand 注解中，还可以通过 commandProperties、threadPoolProperties 属性来设置命令的配置。

Hystrix 示例如下：

• 创建项目

  创建名称为 spring-cloud-hystrix-client 的 Spring Cloud 项目，因为项目示例使用到了 Ribbon 因此也增加了相关依赖，修改 POM.xml 中增加以下依赖项：

  <?xmlversion="1.0"encoding="UTF-8"?>

  <projectxmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0http://maven.apache.org/xsd/maven-4.0.0.xsd">

  <modelVersion>4.0.0</modelVersion>

   
   

  <groupId>org.lixue</groupId>

  <artifactId>spring-cloud-hystrix-client</artifactId>

  <version>0.0.1-SNAPSHOT</version>

  <packaging>jar</packaging>

   
   

  <name>spring-cloud-hystrix-client</name>

  <description>DemoprojectforSpringBoot</description>

   
   

  <parent>

  <groupId>org.springframework.boot</groupId>

  <artifactId>spring-boot-starter-parent</artifactId>

  <version>1.5.4.RELEASE</version>

  <relativePath/><!--lookupparentfromrepository-->

  </parent>

   
   

  <properties>

  <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

  <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>

  <java.version>1.8</java.version>

  <spring-cloud.version>Dalston.SR5</spring-cloud.version>

  </properties>

   
   

  <dependencies>

  <dependency>

  <groupId>org.springframework.boot</groupId>

  <artifactId>spring-boot-starter-web</artifactId>

  </dependency>

  <dependency>

  <groupId>org.springframework.cloud</groupId>

  <artifactId>spring-cloud-starter-eureka</artifactId>

  </dependency>

  <dependency>

  <groupId>org.springframework.cloud</groupId>

  <artifactId>spring-cloud-starter-ribbon</artifactId>

  </dependency>

  <dependency>

  <groupId>org.springframework.cloud</groupId>

  <artifactId>spring-cloud-starter-hystrix</artifactId>

  </dependency>

  <dependency>

  <groupId>org.springframework.boot</groupId>

  <artifactId>spring-boot-starter-test</artifactId>

  <scope>test</scope>

  </dependency>

  </dependencies>

   
   

  <dependencyManagement>

  <dependencies>

  <dependency>

  <groupId>org.springframework.cloud</groupId>

  <artifactId>spring-cloud-dependencies</artifactId>

  <version>${spring-cloud.version}</version>

  <type>pom</type>

  <scope>import</scope>

  </dependency>

  </dependencies>

  </dependencyManagement>

   
   

  <build>

  <plugins>

  <plugin>

  <groupId>org.springframework.boot</groupId>

  <artifactId>spring-boot-maven-plugin</artifactId>

  </plugin>

  </plugins>

  </build>

  </project>

   
   

• 创建服务调用

  对于一些默认配置，例如命令组的 Key 等，可以使用 @DefaultProperties 注解标注到类，这样就减少了 @HystrixCommand 注解的配置代码量

  package org.lixue;

   
   

  import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;

  import org.springframework.beans.factory.annotation.Autowired;

  import org.springframework.stereotype.Component;

  import org.springframework.web.client.RestTemplate;

   
   

  @DefaultProperties(groupKey="hello-world")

  @Component

  public class HelloWorldClient{

   
   

  @Autowired

  private RestTemplate restTemplate;

   
   

  @HystrixCommand(fallbackMethod="speakFallback",commandKey="hello-world",

  threadPoolKey="hello-world",

  commandProperties={

  @HystrixProperty(name="execution.isolation.thread.timeoutInMilliseconds",value="500")

  },

  threadPoolProperties={

  @HystrixProperty(name="coreSize",value="50")

  }

  )

  public String speak(Stringname){

  if(name==null ||"".equals(name)){

  name="null";

  }

   
   

  return restTemplate.getForObject("http://HELLOWORLD-PROVIDER/speaks?names="+name,String.class);

  }

   
   

  private String speakFallback(String name){

  return"call error,name is "+name;

  }

  }

   
   

• 创建 REST 服务

  在服务调用类中声明 HelloWorldFeignClient 类的实例，并使用 @Autowired 注解标注，表示使用 Spring 的自动注入实例，在

  package org.lixue;

   
   

  import org.springframework.beans.factory.annotation.Autowired;

  import org.springframework.web.bind.annotation.RequestMapping;

  import org.springframework.web.bind.annotation.RequestMethod;

  import org.springframework.web.bind.annotation.RequestParam;

  import org.springframework.web.bind.annotation.RestController;

   
   

  @RestController

  public class InvokerController{

   
   

  @Autowired

  private HelloWorldClient helloWorldClient;

   
   

  @RequestMapping(method=RequestMethod.GET,path="/speak")

  public String speak(@RequestParam("name")Stringname){

  return helloWorldClient.speak(name);

  }

  }

• 修改启动类

  package org.lixue;

   
   

  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.client.loadbalancer.LoadBalanced;

  import org.springframework.cloud.netflix.feign.EnableFeignClients;

  import org.springframework.context.annotation.Bean;

  import org.springframework.web.client.RestTemplate;

   
   

  @SpringBootApplication

  @EnableDiscoveryClient

  @EnableCircuitBreaker

  public class SpringCloudHystrixClientApplication{

   
   

  public static void main(String[]args){

  SpringApplication.run(SpringCloudHystrixClientApplication.class,args);

  }

   
   

  @LoadBalanced

  @Bean

  publicRestTemplate restTemplate(){

  return new RestTemplate();

  }

  }

   
   

• 增加配置

  #配置应用名称

  spring:

  application:

  name:spring-cloud-hystrix-client

  #服务端口

  server:

  #设置eureka服务注册中心的地址，如果多个以逗号分割

  eureka:

  client:

  service-url:

  defaultZone:http://eurekaserver01:9000/eureka/,http://eurekaserver02:9000/eureka/

   
   

   
   

• 测试验证

  由于我们使用了 Ribbon 因此首先启动 eureka-server 和 service-provider 服务，然后启动该项目，访问 http://localhost:8077/speak?name=abc 可以看到能正常返回信息，如下：

  {"abc":"Hello World abc Port=8002"}

  这时关闭 service-provider 服务，再次访问这时返回的是我们 speakFallback 方法返回的信息，表示调用出错 Hystrix 进行和回退，如下：

  call error,name is abc