System.setProperty("fess.version", version);
            System.setProperty("fess.product.version", productVersion);
        } catch (final Exception e) {
            throw new FessSystemException("Failed to parse project.properties.", e);
        }
    }

    @PreDestroy
    public void destroy() {
        shutdownHookList.forEach(action -> {
            try {

     * @throws ConfigPropertyNotFoundException When the property is not found.
     */
    String get(String propertyKey);

    /**
     * Is the property true?
     * @param propertyKey The key of the property which is boolean type. (NotNull)
     * @return The determination, true or false. (if not found, exception)

     */
    protected void assertPropertyNotNull(String property) {
        if (property == null) {
            String msg = "The argument 'property' for message should not be null.";
            throw new IllegalArgumentException(msg);
        }
    }