springCloud 集成feign

以A（消费者）服务远程调用B（生产者）服务为例

1. A,B服务引入依赖

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

2.A,B服务启动类上添加@EnableFeignClients注解开启Spring Cloud Feign的远程支持功能

/**
 * 类说明:
 *
 * @author wqf
 * @date 2021/7/9 17:54
 */
@EnableFeignClients(basePackages = {"pers.darcy.flower.gateway.service.feign.api"})
@SpringBootApplication
public class GatewayServiceApplication {
    public static void main(String[] args) {
        SpringApplication.run(GatewayServiceApplication.class);
    }

    //处理feign远程调用报错：No qualifying bean of type ‘org.springframework.boot.autoconfigure.http.HttpMessage...
    @Bean
    @ConditionalOnMissingBean
    public HttpMessageConverters messageConverters(ObjectProvider<HttpMessageConverter<?>> converters) {
        return new HttpMessageConverters(converters.orderedStream().collect(Collectors.toList()));
    }
}

3.A服务编写远程调用接口

@FeignClient(value = "account-server", fallback = AuthPermissionFeignBack.class)
public interface AuthPermissionFeignApi {

    /**
     * 方法描述: 查询用户id
     *
     * @param userId 用户id
     * @return java.util.List<pers.darcy.flower.account.api.dto.PermissionDTO>
     * @author wqf
     * @date 2022/2/22 14:04
     */
    @GetMapping(value = "/user/permissions/{userId}")
    List<PermissionDTO> listUserPermissions(@PathVariable("userId") Long userId);
}

说明：

1. account-server B服务名称（被调用方服务名称 spring.application.name）
   接口上添加注解：@FeignClient
2. fallback = AuthPermissionFeignBack.class 表示方法的降级，当该接口方法出现错误，将会走AuthPermissionFeignBack类中的实现
3. @PathVariable("userId") 不可以写成@PathVariable，就算参数名和接口中的一样， 否则会报错
4. @GetMapping(value = "/user/permissions/{userId}") 接口路径和B服务的接口路径保持一致

AuthPermissionFeignBack.java

@Slf4j
public class AuthPermissionFeignBack implements AuthPermissionFeignApi {
    @Override
    public List<PermissionDTO> listUserPermissions(Long userId) {
        log.info("-----服务降级-----");
        return null;
    }
}

4.B 写接口

@Slf4j
@RestController
@RequestMapping(value = "/user")
public class UserController {
    @GetMapping(value = "/permissions/{userId}")
    public List<PermissionDTO> listUserPermissions(@PathVariable Long userId) {
        PermissionDTO permissionDTO = new PermissionDTO();
        permissionDTO.setId(1L);
        return Collections.singletonList(permissionDTO);
    }
}

以上应该就可以了