How to use Custom Type as form type with REST API how to do setup in camunda moduler and how to use it inside the Java to create /get that Custom variables in/using Java /java class to retreive it

How to use Custom Type as form type with REST API how to do setup in camunda moduler and how to use it inside the Java to create /get that Custom form variables in/using Java /java class to retreive it and which type of form variables actually we can use any example of it ?

i am trying for the double but am not able to start the my spring boot application either due to this… how can we proceed on this CustomTypes