How to create own custom field type if I need a Combobox?

Dear Community,

I need to create my own custom field type which is a combobox but I am struggeling a little bit. I already created successfully a normal “textbox” customfield, which means, my class “extends GenericTextCFType”.

So far so good. Does anyone have a small Java example of how to set up a combobox? Creating a combobox in velocity is quite easy of course, but I think I have to tell Jira inside of my Java code that it has to expect a combobox and not a textbox.

Kind regards for your help/hint.
Manuel