背景
springcloud:finchley.release
简介
Feign是SpringCloud体系中声明式Rest客户端，通过简单配置、创建接口和注解即可实现Restful服务的调用。而且开始支持SpringMvc了。
简单应用
依赖：org.springframework.cloud:spring-cloud-starter-openfeign
入口加@EnableFeignClients注解
创建相应接口、加注解
//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);
}开启Feign断路器和上下文支持
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断路器回调
断路器支持回退，就是当断路器开启或接口出现错误时执行回调定义的方法，返回预先定义好的结果。 开启回调支持只需在@FeignClient注解中配置fallback参数为接口的回调实现类，并且回调实现类要被注解为Spring Bean(可以通过@Component，@Service等注解实现，详情见Spring4的注解文档)。
@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");
}
}如果需要知道回退原因可以通过回退工厂来实现，代码实例如下：
@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支持继承接口
Feign支持接口继承的方式，将操作通过接口来形成契约。
//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 {}压缩支持
开启压缩可以有效节约网络资源，但是会增加CPU压力，建议把最小压缩的文档大小适度调大一点
//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
日志配置
消费服务的接口所在包，必须是debug
# 日志支持logging.level.project.user.UserClient: DEBUG
定义自定义配置类,定义日志级别
@Configurationpublic class FooConfiguration {
@Bean
Logger.Level feignLoggerLevel() {
return Logger.Level.FULL;
}
}日志级别
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.
