1.引入依賴

Maven座標

<!--feign 依賴-->
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-openfeign</artifactId>
    <version>${feign.version}</version>
</dependency>

2. 定義FeignClient

/**
 * @description:  基礎服務
 *
 * FeignClient註解：
 * name/value屬性: 這兩個的作用是一樣的,指定的是呼叫服務的微服務名稱（獨立使用時，只需唯一） 可以使用環境變數或者jvm屬性定義url欄位
 * url： 定義遠端服務的domain
 * fallbackFactory: 定義熔斷器（可以在熔斷器中定義熔斷處理，返回兜底的結果）
 *
 * @date: 2020/11/24 14:49
 * @author: fdh
 */
//@FeignClient(name = "baseSapi", url = "${qs.sapi.base.url.prefix}", fallbackFactory = RemoteBaseFallBackFactory.class)
@FeignClient(name = "baseSapi", url = "http://localhost:9001", fallbackFactory = RemoteBaseFallBackFactory.class)
public interface RemoteBaseService {

    /**
     * 獲取考季知識點
     *
     * 介面地址： http:// xxxxx
     *
     * @param seasonId
     * @return
     */
    @RequestMapping(value = "/s1/v1/seasonKnowledgePoint/kpListBySeasonId", method = RequestMethod.GET)
    SapiResult<List<KnowledgePointVo>> getKpListBySeasonId(@RequestParam("seasonId") Long seasonId);
}

3.定義熔斷器

/**
 * @description:  遠端基礎熔斷工廠
 * @date: 2020/11/25 13:48
 * @author: fdh
 */
@Component
public class RemoteBaseFallBackFactory implements FallbackFactory<RemoteBaseService> {

    @Override
    public RemoteBaseService create(Throwable throwable) {
        RemoteBaseFallBackServiceImpl remoteBaseFallBackService = new RemoteBaseFallBackServiceImpl();
        remoteBaseFallBackService.setThrowable(throwable);
        return remoteBaseFallBackService;
    }
}

4.定義FeignClient熔斷實現

/**
 * @description:  RemoteBaseService熔斷處理
 * @date: 2020/11/25 13:49
 * @author: fdh
 */
public class RemoteBaseFallBackServiceImpl implements RemoteBaseService {

    private static final Logger log = LoggerFactory.getLogger(RemoteBaseFallBackServiceImpl.class);

    @Setter
    private Throwable throwable;

    private void printLog(String modules, Throwable throwable){
        if( modules == null ){
            modules = StringUtils.EMPTY;
        }
        log.info("{}異常:", modules, throwable);
    }

    @Override
    public SapiResult<List<KnowledgePointVo>> getKpListBySeasonId(Long seasonId) {
        printLog("知識點介面", throwable);
        return SapiResultUtil.success(Collections.emptyList());
    }
}

5. 掃描FeignClient

/**
 * @description:  啟動類
 * @date: 2020/11/25 13:52
 * @author: fdh
 */
@SpringBootApplication
@EnableFeignClients(basePackages = "com.xxx.feign")
public class DaApplication extends SpringBootServletInitializer {
    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        return application.sources(DaApplication.class);
    }

    public static void main(String[] args) {
        SpringApplication.run(DaApplication.class, args);
    }
}

以上就可以實現Feign獨立使用，不依賴註冊中心，進行獨立遠端呼叫

補充：

1. 生產環境上往往需要記錄FeignClient遠端呼叫日誌，我們可以定義日誌輸出級別

/**
 * @description:  Feign日誌
 * @date: 2020/11/5 16:35
 * @author: fdh
 */
@Configuration
public class FeignConfig {
    @Bean
    Logger.Level feignLoggerLevel() {
        return Logger.Level.FULL;
    }
}

推薦日誌級別：

2. 啟用熔斷並設定熔斷超時時間（預設1秒）

feign.hystrix.enabled=true
hystrix.command.default.execution.isolation.thread.timeoutInMilliseconds: 30000

統一處理，需要增加FeignClient遠端呼叫攜帶加密引數

@Component
public class FeignRequestInterceptor implements RequestInterceptor {

    private org.slf4j.Logger log = LoggerFactory.getLogger(FeignRequestInterceptor.class);
    
    @Override
    public void apply(RequestTemplate requestTemplate) {
        try {
            // xxxx 演算法
            //String sign = DigestUtils.md5DigestAsHex(params.getBytes("utf-8"));
            requestTemplate.query("sign", "xxxxxx");
        } catch (UnsupportedEncodingException e) {
            log.error("簽名失敗：", e);
        }
    }
    
}