Loading of FXML files with custom controls - how to handle missing classes?

[Oliver-Loeffler]

Hello all,

what is the supposed behavior for Scene Builder when loading FXML files with custom controls or controllers/data types?
There are some cases where the problem is, that the FXMLs to be loaded have custom imports and those imports are not available to Scene Builder by default.

Currently there is an Exception generated and shown to the user. Its cause is then ideally a java.lang.ClassNotFoundException:. The way this is presented to the user is more than sub optimal.

What would be a good way to handle this?

1. Show a custom notification window and explain whats missing and how to deal with it?
2. Skim through all FXML files (also through includes) and collect a list of all possibly missing classes - then instruct user how to proceed?
3. Skim through all FXML files and replace unknown includes/classes by a placeholder control so that missing imports/controls can be indicated in GUI (e.g. using a red rectangle which provides a proper tooltip or text).
4. Skim through all FXML files and replace unknown includes/classes, display to user and allow user to update JAR/FXML Manager so that custom components are available before attempt to finally load the FXML.

Feedback appreciated!
Thanks!