spring cloud2.0 study notes Feign practice

Background

• springCloud:Finchley.RELEASE

Introduction

Feign is a declarative Rest client in the Spring Cloud system. It can call Restful services through simple configuration, creation of interfaces and annotations. And it starts to support SpringMvc.

Simple application

• Dependency: org.springframework.cloud:spring-cloud-starter-openfeign

• Entry plus @ EnableFeignClients annotation

• Create the corresponding interface and add annotation

//入口类
@SpringBootApplication
@EnableFeignClientspublic class Application {

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

}
//原型接口声明
@FeignClient("stores")public interface StoreClient {
    @RequestMapping(method = RequestMethod.GET, value = "/stores")
    List<Store> getStores();    
    @RequestMapping(method = RequestMethod.POST, value = "/stores/{storeId}", consumes = "application/json")
    Store update(@PathVariable("storeId") Long storeId, Store store);
}

Enable Feign circuit breaker and context support

• feign.hystrix.enabled=true

# To disable Hystrix in Feignfeign:
  hystrix:
    enabled: true# To set thread isolation to SEMAPHORE# 将断路器隔离级别由默认的线程隔离调整为信号灯hystrix:
  command:    default:
      execution:
        isolation:
          strategy: SEMAPHORE

Circuit breaker callback

The circuit breaker supports fallback, which means that the callback definition is executed when the circuit breaker is turned on or an error occurs on the interface. Method that returns predefined results. To enable callback support, you only need to configure the fallback parameter in the @FeignClient annotation to be the callback implementation class of the interface, and the callback implementation class must be annotated as a Spring Bean (can be implemented through @Component, @Service and other annotations, see the annotation documentation of Spring 4 for details).

@FeignClient(name = "hello", fallback = HystrixClientFallback.class)
protected interface HystrixClient {
    @RequestMapping(method = RequestMethod.GET, value = "/hello")
    Hello iFailSometimes();
}

@Componentstatic class HystrixClientFallback implements HystrixClient {
    @Override    
    public Hello iFailSometimes() {        
        return new Hello("fallback");
    }
}

If you need to know the reason for the rollback, you can use the rollback factory. The code example is as follows:

@FeignClient(name = "hello", fallbackFactory = HystrixClientFallbackFactory.class)
protected interface HystrixClient {
    @RequestMapping(method = RequestMethod.GET, value = "/hello")
    Hello iFailSometimes();
}

@Componentstatic class HystrixClientFallbackFactory implements FallbackFactory<HystrixClient> {
    @Override    public HystrixClient create(Throwable cause) {        
        return new HystrixClient() {
            @Override            
            public Hello iFailSometimes() {                
                return new Hello("fallback; reason was: " + cause.getMessage());
            }
        };
    }
}

Feign supports interface inheritance

Feign supports interface inheritance. Operations form contracts through interfaces.

//生产者的控制层接口public interface UserService {

    @RequestMapping(method = RequestMethod.GET, value ="/users/{id}")
    User getUser(@PathVariable("id") long id);
}
//生产者的控制器实现
@RestController
public class UserResource implements UserService {}
//消费端的Feign接口定义
package project.user;
@FeignClient("users")
public interface UserClient extends UserService {}

Compression support

Enabling compression can effectively save network resources, but it will increase CPU pressure. It is recommended to increase the minimum compressed document size appropriately

//开启压缩
feign.compression.request.enabled=true
feign.compression.response.enabled=true

//配置压缩文档类型及最小压缩的文档大小
feign.compression.request.mime-types=text/xml,application/xml,application/json
feign.compression.request.min-request-size=2048

Log configuration

• The package where the interface of the consumer service is located must be debug

# 日志支持logging.level.project.user.UserClient: DEBUG

• Define a custom configuration class and define the log level

@Configurationpublic class FooConfiguration {
    @Bean
    Logger.Level feignLoggerLevel() {        
        return Logger.Level.FULL;
    }
}

• Log level
  

• ##NONE, No logging (DEFAULT).

• BASIC, Log only the request method and URL and the response status code and execution time.

##HEADERS, Log the basic information along with request and response headers .
FULL, Log the headers, body, and metadata for both requests and responses.

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