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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

  
      org.springframework.cloud
      spring-cloud-starter-netflix -eureka-client
  
  
      org.springframework.cloud
      spring-cloud-starter-openfeign
  
  
      org.springframework.boot
      spring-boot-starter-web
  
  

  • application.yml配置

    server:
      port: 8701
    spring:
      application:
        name: feign-service
    eureka:
      client:
        register-with-eureka: true
        fetch-registry: true
        service-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 getUser(@PathVariable Long id);
        }
        

        • 添加UserFeignController调用UserService实现服务调用

          @RestController
          @RequestMapping("/user")
          public class UserFeignController {
              @Autowired
              private 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 {
      @Override
      public CommonResult create(User user) {
          User defaultUser = new User(-1L, "defaultUser", "123456");
          return new CommonResult<>(defaultUser);
      }
      @Override
      public CommonResult getUser(Long id) {
          User defaultUser = new User(-1L, "defaultUser", "123456");
          return new CommonResult<>(defaultUser);
      }
      @Override
      public CommonResult getByUsername(String username) {
          User defaultUser = new User(-1L, "defaultUser", "123456");
          return new CommonResult<>(defaultUser);
      }
      @Override
      public CommonResult update(User user) {
          return new CommonResult("调用失败，服务被降级",500);
      }
      @Override
      public 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 {
      @Bean
      Logger.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Hystrix
  compression:
    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

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