OpenFeign常用操作

一、OpenFeign简介

OpenFeign是Spring Cloud的声明式HTTP客户端，简化了微服务间的HTTP调用。

特点：

声明式调用，面向接口编程
集成Ribbon实现负载均衡
集成Sentinel实现服务熔断
支持Spring MVC注解

二、基本使用

添加依赖

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>

启用Feign

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

定义Feign客户端

@FeignClient(name = "user-service")
public interface UserClient {

    @GetMapping("/user/{id}")
    User getUserById(@PathVariable("id") Long id);

    @PostMapping("/user")
    User createUser(@RequestBody User user);

    @PutMapping("/user")
    User updateUser(@RequestBody User user);

    @DeleteMapping("/user/{id}")
    void deleteUser(@PathVariable("id") Long id);
}

使用Feign客户端

@Service
public class OrderService {

    @Autowired
    private UserClient userClient;

    public Order getOrderDetail(Long orderId) {
        Order order = orderMapper.selectById(orderId);
        User user = userClient.getUserById(order.getUserId());
        order.setUserName(user.getName());
        return order;
    }
}

三、配置

超时配置

feign:
  client:
    config:
      default:  # 全局配置
        connectTimeout: 5000
        readTimeout: 10000
      user-service:  # 特定服务配置
        connectTimeout: 3000
        readTimeout: 5000

日志配置

日志级别：

NONE：无日志（默认）
BASIC：请求方法、URL、响应状态码、执行时间
HEADERS：BASIC + 请求和响应头
FULL：HEADERS + 请求和响应体

feign:
  client:
    config:
      user-service:
        loggerLevel: FULL

// 需要设置Feign客户端的日志级别为DEBUG
@Configuration
public class FeignLogConfig {
    @Bean
    Logger.Level feignLoggerLevel() {
        return Logger.Level.FULL;
    }
}

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logging:
  level:
    com.example.feign.UserClient: DEBUG

拦截器

@Component
public class FeignAuthInterceptor implements RequestInterceptor {

    @Override
    public void apply(RequestTemplate template) {
        // 添加认证头
        ServletRequestAttributes attributes = 
            (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
        if (attributes != null) {
            HttpServletRequest request = attributes.getRequest();
            String token = request.getHeader("Authorization");
            if (token != null) {
                template.header("Authorization", token);
            }
        }
    }
}

feign:
  client:
    config:
      default:
        requestInterceptors:
          - com.example.interceptor.FeignAuthInterceptor

四、熔断降级

添加Sentinel依赖

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-alibaba-sentinel</artifactId>
</dependency>

启用Sentinel

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feign:
  sentinel:
    enabled: true

定义降级类

@FeignClient(name = "user-service", fallback = UserClientFallback.class)
public interface UserClient {

    @GetMapping("/user/{id}")
    User getUserById(@PathVariable("id") Long id);
}

@Component
public class UserClientFallback implements UserClient {

    @Override
    public User getUserById(Long id) {
        User user = new User();
        user.setId(id);
        user.setName("默认用户");
        return user;
    }
}

定义降级工厂

可获取异常信息：

@FeignClient(name = "user-service", fallbackFactory = UserClientFallbackFactory.class)
public interface UserClient {

    @GetMapping("/user/{id}")
    User getUserById(@PathVariable("id") Long id);
}

@Component
public class UserClientFallbackFactory implements FallbackFactory<UserClient> {

    @Override
    public UserClient create(Throwable cause) {
        return new UserClient() {
            @Override
            public User getUserById(Long id) {
                log.error("调用用户服务失败: {}", cause.getMessage());
                User user = new User();
                user.setId(id);
                user.setName("降级用户");
                return user;
            }
        };
    }
}

五、请求压缩

feign:
  compression:
    request:
      enabled: true
      mime-types: text/xml, application/xml, application/json
      min-request-size: 2048
    response:
      enabled: true

六、文件上传

添加依赖

<dependency>
    <groupId>io.github.openfeign.form</groupId>
    <artifactId>feign-form-spring</artifactId>
</dependency>

配置

@Configuration
public class FeignMultipartConfig {

    @Bean
    @Primary
    @Scope("prototype")
    public Encoder multipartFormEncoder() {
        return new SpringFormEncoder(new SpringEncoder(new ObjectFactory<HttpMessageConverters>() {
            @Override
            public HttpMessageConverters getObject() {
                return new HttpMessageConverters(new RestTemplate().getMessageConverters());
            }
        }));
    }
}

使用

@FeignClient(name = "file-service", configuration = FeignMultipartConfig.class)
public interface FileClient {

    @PostMapping(value = "/upload", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
    String upload(@RequestPart("file") MultipartFile file);
}

七、GET请求传递对象

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// 使用@SpringQueryMap
@GetMapping("/user/list")
List<User> listUsers(@SpringQueryMap UserQuery query);

八、Feign性能优化

使用HttpClient替换默认客户端

<dependency>
    <groupId>io.github.openfeign</groupId>
    <artifactId>feign-httpclient</artifactId>
</dependency>

feign:
  httpclient:
    enabled: true
    max-connections: 200
    max-connections-per-route: 50

连接池配置

@Configuration
public class HttpClientConfig {

    @Bean
    public HttpClient httpClient() {
        RequestConfig requestConfig = RequestConfig.custom()
            .setConnectTimeout(5000)
            .setSocketTimeout(10000)
            .build();
        
        return HttpClientBuilder.create()
            .setMaxConnTotal(200)
            .setMaxConnPerRoute(50)
            .setDefaultRequestConfig(requestConfig)
            .build();
    }
}

九、总结

OpenFeign要点：

声明式调用，简化HTTP通信
合理配置超时和日志
集成Sentinel实现熔断降级
使用连接池提升性能
拦截器统一处理请求头

OpenFeign是微服务间通信的核心组件，掌握其使用是微服务开发的基础。