@Override
    public Boolean parseValue(String value) throws GuacamoleException {

        // If no property provided, return null.
        if (value == null)
            return null;

        // If "true", return true
        if (value.equalsIgnoreCase("true"))
            return true;

        // If "false", return false
        if (value.equalsIgnoreCase("false"))
            return false;

        // Otherwise, fail
        throw new GuacamoleServerException("Property \"" + getName()
                + "\" must be either \"true\" or \"false\".");

    }
A GuacamoleProperty whose value is an boolean. Legal true values are "true",
or "false". Case does not matter.
guacamole-ext/src/main/java/org/apache/guacamole/properties/BooleanGuacamoleProperty.java