protected static String getRequiredProperty(String propertyName) {
		String value = getOptionalProperty(propertyName);
		if(value == null)
			throw new SettingNotFoundException("The property " + propertyName + " is not defined.");
		return value;
	}
protected static String getRequiredProperty ( String propertyName ) { String value = getOptionalProperty ( propertyName ) ; if ( value == null ) throw new SettingNotFoundException ( "The property " + propertyName + " is not defined." ) ; return value ; }
@param propertyName the name of the property
@return the value of the required property (might be an empty string)
@throws SettingNotFoundException if the property cannot be found