Spring Cloud OpenFeign：基于Ribbon和Hystrix的声明式服务调用

Spring Cloud OpenFeign是一个声明式的服务调用框架，基于Feign并整合了Ribbon和Hystrix；目标是简化分布式系统中编写服务间调用的代码，并提供一种更加优雅和便捷的方式来进行服务之间的通信

创建feign-service模块

依赖导入

<dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-netflix -eureka-client</artifactId>
</dependency>
<dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>
<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId>
</dependency>

application.yml配置

server:port: 8701
spring:application:name: feign-service
eureka:client:register-with-eureka: truefetch-registry: trueservice-url:defaultZone: http://localhost:8001/eureka/

启动类上添加@EnableFeignClients注解来启用Feign的客户端功能

@EnableFeignClients
@EnableDiscoveryClient
@SpringBootApplication
public class FeignServiceApplication {public static void main(String[] args) {SpringApplication.run(FeignServiceApplication.class, args);}
}

添加UserService接口完成对user-service服务的接口绑定

@FeignClient(value = "user-service")
public interface UserService {@PostMapping("/user/create")CommonResult create(@RequestBody User user);@GetMapping("/user/{id}")CommonResult<User> getUser(@PathVariable Long id);
}

添加UserFeignController调用UserService实现服务调用

@RestController
@RequestMapping("/user")
public class UserFeignController {@Autowiredprivate UserService userService;@PostMapping("/create")public CommonResult create(@RequestBody User user) {return userService.create(user);}@GetMapping("/{id}")public CommonResult getUser(@PathVariable Long id) {return userService.getUser(id);}
}

Feign中的服务降级

微服务架构中，服务降级是一种应对高并发或系统故障的策略，用于保证系统的可用性和稳定性；Feign是一个声明式的Web服务客户端，可以与Spring Cloud等微服务框架集成，简化服务之间的调用

添加服务降级实现类UserFallbackService

@Component
public class UserFallbackService implements UserService {@Overridepublic CommonResult create(User user) {User defaultUser = new User(-1L, "defaultUser", "123456");return new CommonResult<>(defaultUser);}@Overridepublic CommonResult<User> getUser(Long id) {User defaultUser = new User(-1L, "defaultUser", "123456");return new CommonResult<>(defaultUser);}@Overridepublic CommonResult<User> getByUsername(String username) {User defaultUser = new User(-1L, "defaultUser", "123456");return new CommonResult<>(defaultUser);}@Overridepublic CommonResult update(User user) {return new CommonResult("调用失败，服务被降级",500);}@Overridepublic CommonResult delete(Long id) {return new CommonResult("调用失败，服务被降级",500);}
}

修改UserService接口，设置服务降级处理类为UserFallbackService

@FeignClient(value = "user-service",fallback = UserFallbackService.class)
public interface UserService {
}

修改application.yml，开启Hystrix功能

feign:hystrix:enabled: true #在Feign中开启Hystrix

日志打印功能

Feign提供了日志打印功能，我们可以通过配置来调整日志级别，从而了解Feign中Http请求的细节

日志级别

NONE：默认的，不显示任何日志
BASIC：仅记录请求方法、URL、响应状态码及执行时间
HEADERS：除了BASIC中定义的信息之外，还有请求和响应的头信息
FULL：除了HEADERS中定义的信息之外，还有请求和响应的正文及元数据

通过配置开启更为详细的日志

通过java配置来使Feign打印最详细的Http请求日志信息
@Configuration
public class FeignConfig {@BeanLogger.Level feignLoggerLevel() {return Logger.Level.FULL;}
}
application.yml中配置需要开启日志的Feign客户端；配置UserService的日志级别为debug
logging:level:com.macro.cloud.service.UserService: debug

Feign的常用配置

feign:hystrix:enabled: true #在Feign中开启Hystrixcompression:request:enabled: false #是否对请求进行GZIP压缩mime-types: text/xml,application/xml,application/json #指定压缩的请求数据类型min-request-size: 2048 #超过该大小的请求会被压缩response:enabled: false #是否对响应进行GZIP压缩
logging:level: #修改日志级别com.macro.cloud.service.UserService: debug