Spring Cloud 2-Hystrix 断路容错保护(四)

Spring Cloud  Hystrix 

• 1.RestTemplate 容错
  • pom.xml
  • application.yml
  • application.java
  • HelloService.java
  • Controller.java
• 2.FeignClient 容错
  • pom.xml
  • application.yml
  • Application.java
  • ServiceClient.java
  • Fallback.java

容错保护就是当请求的服务报错或者超时时,可以优雅降级.介绍两种实现:

• RestTemplate 容错
• FeignClient 容错

1.RestTemplate 容错

pom.xml

<!-- hystrix 断路器 -->
<dependency>
   <groupId>org.springframework.cloud</groupId>
   <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
</dependency>

application.yml

spring:
  application:
    name: hystrix-client

server:
  port: 8091

application.java

@EnableCircuitBreaker
@SpringBootApplication
public class HystrixClientApplication {

 @Bean
 @LoadBalanced
 RestTemplate restTemplate(){
  return new RestTemplate();
 }

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

}

@EnableCircuitBreaker 开启断路器功能

HelloService.java

@Service
public class HelloService {

  @Autowired
  private RestTemplate template;

  @HystrixCommand(fallbackMethod = "errorCallback")
  public String hello(){
    return template.getForObject("http://HELLO-SERVICE/hello",String.class);
  }

  public String errorCallback(){
    return "error";
  }

}

• @HystrixCommand(fallbackMethod = "errorCallback") fallbackMethod 指定报错回调
• errorCallback 错误回调方法

Controller.java

@RestController
@RequestMapping("hystrix")
public class HystrixHelloController {

  @Autowired
  private HelloService helloService;

  @GetMapping("hi")
  public String hi(){
    return helloService.hello();
  }
}

访问: http://localhost:8091/hystrix/hi
Hello World!
关闭服务在访问
访问: http://localhost:8091/hystrix/hi
error

2.FeignClient 容错

pom.xml

<!-- feign 声明式服务调用 -->
<dependency>
   <groupId>org.springframework.cloud</groupId>
   <artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>

application.yml

spring:
  application:
    name: hystrix-client

server:
  port: 8091

feign:
  hystrix:
    enabled: true

Application.java

@EnableFeignClients
@EnableCircuitBreaker
@SpringBootApplication
public class HystrixClientApplication {

 @Bean
 @LoadBalanced
 RestTemplate restTemplate(){
  return new RestTemplate();
 }

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

}

必须同时开启断路器@EnableCircuitBreaker和feign客户端@EnableFeignClients

ServiceClient.java

@FeignClient(value = "hello-service", fallback = HystrixClientFallback.class)
public interface HelloServiceClient {

  @RequestMapping(method = RequestMethod.GET, value = "/hello")
  String hello();

}

fallback 指定回调的类

Fallback.java

@Component
public class HystrixClientFallback implements HelloServiceClient {

  @Override
  public String hello() {
    return "error-feign";
  }

}

访问: http://localhost:8091/hystrix/he
Hello World!
关闭服务再访问:
访问: http://localhost:8091/hystrix/he
error-feign