protected Object getEnclosingInstance(Object target) {
        if (!(target instanceof EnclosingInstanceAccessor)) {
            if (isDebug) {
                logger.debug("Invalid target object. Need field accessor({}).", EnclosingInstanceAccessor.class.getName());
            }
            return null;
        } else {
            return ((EnclosingInstanceAccessor) target)._$PINPOINT$_getEnclosingInstance();
        }
    }
for hystrix-core above 1.4

Created by jack on 4/21/16.
agent-module/plugins/hystrix/src/main/java/com/navercorp/pinpoint/plugin/hystrix/interceptor/HystrixObservableCallInterceptor.java