前言

本小節我們學習一下如何是Feign擁有Hystrix的熔斷功能。

案例

• Eureka Server端編寫(參考前例)。
  

• Eureka Client端服務提供方編寫。

  • 專案結構
    

  • CoreCode

    <?xml version="1.0" encoding="UTF-8"?>
    <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    	<modelVersion>4.0.0</modelVersion>
    
    	<artifactId>microservice-deal-broker-cloud-hystrix-with-feign</artifactId>
    	<packaging>jar</packaging>
    
    	<name>microservice-deal-broker-cloud-hystrix-with-feign</name>
    	<description>Demo project for Spring Boot</description>
    
    	<parent>
    		<groupId>com.example</groupId>
    		<artifactId>microservice-deal-parent</artifactId>
    		<version>0.0.1-SNAPSHOT</version>
    	</parent>
    
    	<dependencies>
    		<!-- Eureka -->
    		<dependency>
    			<groupId>org.springframework.cloud</groupId>
    			<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
    		</dependency>
    	
    		<!-- Feignf -->
    		<dependency>
    			<groupId>org.springframework.cloud</groupId>
    			<artifactId>spring-cloud-starter-openfeign</artifactId>
    		</dependency>
    		<!-- springCloud Hystrix依賴 -->
    		<dependency>
    			<groupId>org.springframework.cloud</groupId>
    			<artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
    		</dependency>
    
    	</dependencies>
    
    </project>
    
     
    

    @SpringBootApplication
    @EnableDiscoveryClient
    @EnableFeignClients //開啟FeignClient註解
    @EnableCircuitBreaker //開啟Hystrix熔斷機制
    public class MicroserviceDealBrokerHystrixWithFeignApplication {
    
    	public static void main(String[] args) {
    		SpringApplication.run(MicroserviceDealBrokerHystrixWithFeignApplication.class,
    				args);
    	}
    }
    
     
    

    @FeignClient(name = "microservice-deal-cloud",fallback = HystrixFallBackMethod.class)
    public interface FeignConfig {
    
    	//第一個坑：使用Feign的時候,如果引數中帶有@PathVariable形式的引數,則要用value=""標明對應的引數,否則會丟擲IllegalStateException異常
    	@GetMapping("/deal/{id}")
    	public Deal findById(@PathVariable(value="id") Long id);
    }
    

    @Component
    public class HystrixFallBackMethod implements FeignConfig {
    
    	@Override
    	public Deal findById(Long id) {
    		Deal deal = new Deal();
    		deal.setId(id.intValue());
    		deal.setName("Dustyone");
    		return deal;
    	}
    
    }
    
     
    

    @RestController
    public class BrokerController {
    	
    	@Autowired
    	private FeignConfig feignConfig;
    	
    	@GetMapping("/deal/{id}")
    	public Deal findById(@PathVariable(value="id") Long id) {
    		return this.feignConfig.findById(id);
    	}
    }
    

• Eureka Client端服務提消費編寫(單例項) (參考前例)。

• 訪問：http://localhost:8082/deal/2
  

• 手動shutdown 服務提供者：
  

• 訪問：http://localhost:8082/deal/2
  
  此時FeignClient中宣告的 Hystrix熔斷機制開啟了。

小結

• 在FeignClient中宣告Hystrix熔斷機制需要在@FeignClient中宣告fallback方法，同時配置檔案中宣告Feign對Hystrix的支援：feign:hystrix:enabled: true。
• 在主類中聲明瞭@EnableFeignClients可以不需要對@EnableCircuitBreaker做宣告(feign:hystrix:enabled: true一被宣告)。
• 本小節使用的案例：microservice-deal-eureka、microservice-deal-cloud、microservice-deal-broker-cloud-hystrix-with-feign