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

java 复制代码

<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

yml 复制代码

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

java 复制代码

@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

java 复制代码

@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

java 复制代码

@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
java 复制代码
@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<User> getUser(Long id) {
        User defaultUser = new User(-1L, "defaultUser", "123456");
        return new CommonResult<>(defaultUser);
    }

    @Override
    public CommonResult<User> 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
java 复制代码
@FeignClient(value = "user-service",fallback = UserFallbackService.class)
public interface UserService {
}
修改application.yml，开启Hystrix功能
yml 复制代码
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
java 复制代码
@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
java 复制代码
logging:
  level:
    com.macro.cloud.service.UserService: debug

Feign的常用配置

java 复制代码

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