* Get the value of property as {@link String}.
     * @param propertyKey The key of the property. (NotNull)
     * @return The value of found property. (NotNull: if not found, exception)
     * @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 "cpu";

                default:
                    throw new ConfigPropertyNotFoundException(propertyKey);
                }
            }

            @Override
            public Integer getAsInteger(String propertyKey) {
                String value = get(propertyKey);
                if (value == null) {
                    return null;
                }
                try {

            public String get(String propertyKey) {
                return fessConfig.get(propertyKey);
            }

            @Override
            public BigDecimal getAsDecimal(String propertyKey) {
                return DfTypeUtil.toBigDecimal(get(propertyKey));
            }

            @Override
            public Integer getAsInteger(String propertyKey) {

            private static final long serialVersionUID = 1L;

            @Override
            public String get(String propertyKey) {
                // Check system properties first (with prefix)
                String systemValue = System.getProperty(Constants.FESS_CONFIG_PREFIX + propertyKey);
                if (systemValue != null) {
                    return systemValue;
                }

        // Setup - test message code with different property keys
        final String message = "Query field error";
        final String propertyKey = "searchQuery";
        final VaMessenger<FessMessages> messageCode = messages -> messages.addErrorsInvalidQueryUnknown(propertyKey);

        // Execute
        final InvalidQueryException exception = new InvalidQueryException(messageCode, message);

        // Verify