@FeignClient(name = "foo-service",fallback = FooClient.Fallback.class)
public interface FooClient {
    @GetMapping("/foo/bar")
    Rest<Map<String, String>> bar();

    @Component
    class Fallback implements FooClient {
        @Override
        public Rest<Map<String, String>> bar() {
            return RestBody.fallback();
        }
    }
}

/**
 * 需要注入Spring IoC
 **/
static class BearerTokenRequestInterceptor implements RequestInterceptor {
        @Override
        public void apply(RequestTemplate template) {
            final String authorization = HttpHeaders.AUTHORIZATION;
            Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
            
            if (authentication instanceof JwtAuthenticationToken){
                JwtAuthenticationToken jwtAuthenticationToken = (JwtAuthenticationToken) authentication;
                String tokenValue = jwtAuthenticationToken.getToken().getTokenValue();
                template.header(authorization,"Bearer "+tokenValue);
            }
        }
    }

	Supplier<Future<T>> futureSupplier = () -> executorService.submit(toRun::get);

private Supplier<Object> asSupplier(final Method method, final Object[] args) {
		final RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();
		return () -> {
			try {
				RequestContextHolder.setRequestAttributes(requestAttributes);
				return this.dispatch.get(method).invoke(args);
			}
			catch (RuntimeException throwable) {
				throw throwable;
			}
			catch (Throwable throwable) {
				throw new RuntimeException(throwable);
			}
			finally {
				RequestContextHolder.resetRequestAttributes();
			}
		};
	}

		final RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();

	RequestContextHolder.setRequestAttributes(requestAttributes);

public abstract class RequestContextHolder  {
 
	private static final ThreadLocal<RequestAttributes> requestAttributesHolder =
			new NamedThreadLocal<>("Request attributes");

	private static final ThreadLocal<RequestAttributes> inheritableRequestAttributesHolder =
			new NamedInheritableThreadLocal<>("Request context");
// 省略
}

    /**
     * 令牌中繼
     */
    static class BearerTokenRequestInterceptor implements RequestInterceptor {
        private static final Pattern BEARER_TOKEN_HEADER_PATTERN = Pattern.compile("^Bearer (?<token>[a-zA-Z0-9-._~+/]+=*)$",
                Pattern.CASE_INSENSITIVE);

        @Override
        public void apply(RequestTemplate template) {
            final String authorization = HttpHeaders.AUTHORIZATION;
            ServletRequestAttributes requestAttributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
            if (Objects.nonNull(requestAttributes)) {
                String authorizationHeader = requestAttributes.getRequest().getHeader(HttpHeaders.AUTHORIZATION);
                Matcher matcher = BEARER_TOKEN_HEADER_PATTERN.matcher(authorizationHeader);
                if (matcher.matches()) {
                    // 清除token頭 避免傳染
                    template.header(authorization);
                    template.header(authorization, authorizationHeader);
                }
            }
        }
    }