@FeignClient用于Nacos微服务间的接口调用

依赖：

<!-- spring-boot启动依赖 -->
<!-- 提供者 -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!-- openFeign -->
<!-- 消费者-->
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>

yml配置

feign:
  compression:
    response:
      enabled: true
    request:
      enabled: true
      mime-types: text/xml,application/xml,application/json
      min-request-size: 2048
  circuitbreaker:
    enabled: true
  client:
    config:
      default:
        connectTimeout: 5000
        readTimeout: 5000
        loggerLevel: basic

提供者创建RESTful接口，controller接口 @RestController @GetMapping("/url")

消费者创建feign目录，创建Interface ManagementClient

//name 填写
//spring:
//application:
//  name: management
//springboot的服务名
//fallback填写实现类，用于接口回调，接口异常时返回保底数据
@FeignClient(name = "management", fallback = ManagementClientFallback.class)
public interface ManagementClient {

    @PostMapping("/url")
    OperaResponse selectList(@RequestBody IdRequest request);
}

/feign/impl，创建ManagementClientFallback类

/**
 * fallback是在远程服务调用失败时，向调用方返回一个备用（回退）响应的机制
 */
@Component
public class ManagementClientFallback implements ManagementClient {
    @Override
    public OperaResponse selectList(IdRequest request) {
        return OperaResponse.error(ErrStatus.FEIGN_ERROR);
    }
}

创建ClientUtil用于调用Client方法，service层依赖注入Client，将Client对象和参数传给ClientUtil方法

    @Autowired
    private ChannelManagementClient channelManagementClient;

public class ClientUtil {
    private ClientUtil(){
    }

    public static List<Response> selectList(ManagementClient client, Integer Id){
        IdRequest request = new IdRequest();
        request.setId(id);
        OperaResponse operaResponse = client.selectList(request);
        if(operaResponse.getData() == null){
            return new ArrayList<>();
        }
        List<Response> list = JSONObject.parseArray(JSONObject.toJSONString(operaResponse.getData()), Response.class);
        return list == null ? new ArrayList<>() : list;
    }
}