In short, what do I need to improve so that I can only use postman without a view, send a request and get a response and write a back end?
You need to create servlet.
Have it running on a web server .
Have it handle request and response parameters.
Configure the request in Postman .
Call the request in Postman.
Look at the response .
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In your servlet ,you will likely call another java object/class to package request in one or more model objects, validate the request (model object(s)) ,do any processing ,and then forward the java model data object(s) to the data access layer. The data access layer then persists the data.
Most people use framework like Spring to handle these actions.
Hope this helps.
Paul