html input data validation in spring boot REST API

Question

Hello Friends ,

 

Task 1: 

I have requirement to validate html input data in spring boot REST API.

one input field needs to be check whether exists in database or not while submitting form.

if not exits , needs to send error mesage beside field as "Provide valid Id" 

 

 Task 2 :

same rquirement needs to be worked where form fields built from Javascript  dynamic innerhtml as well.