public static String getPropertyValue(String username, String propertyName) throws UserNotFoundException {
        return UserManager.getUserPropertyProvider().loadProperty( username, propertyName );
    }
Returns the value of the specified property for the given username. This method is
an optimization to avoid loading a user to get a specific property.

@param username the username of the user to get a specific property value.
@param propertyName the name of the property to return its value.
@return the value of the specified property for the given username.
@throws UserNotFoundException Depending on the installed user provider (some will return null instead).
xmppserver/src/main/java/org/jivesoftware/openfire/user/User.java