@Override
        public T create(final Throwable cause) {
            if (logger.isTraceEnabled()) {
                logger.trace("fallback due to: " + cause.getMessage(), cause);
            }
            return constant;
        }
Returns an instance of the fallback appropriate for the given cause.
@param cause cause of an exception.
@return fallback
shenyu-sdk/shenyu-sdk-spring/src/main/java/org/apache/shenyu/sdk/spring/FallbackFactory.java