Are there rules/principles for structuring java servlets in a web application?

Question

Java

Hello! I decided to study the development of web applications in java (I have enough writing desktop applications at work). No frameworks, just a bike, just a hardcore experience. Well, I started with servlets.
Having created a new empty project, I got into a stupor. After all, you need to understand how to correctly structure servlets that create all the html markup ...
Or should servlets not build a complete html page, but only process get and post requests?
And if the servlet builds the page, then how exactly - one servlet per page? or one page is built by several servlets (separated by graphical components, for example - one servlet for the header, the second for the table, the third for the buttons)?
What should run first? index.html or some servlet?
In general, as a person who loves order, I dug into these issues.
I was not commercially involved in web development, only a couple of sites at the university, but then I did not realize the importance of structured code (markup for html).

In what books (or other sources) can you find answers to the questions above?

Answer 1

can find on YouTube a simple course on java ee in which only hardcore (without springs), etc.? All questions are answered there.
For example , Roman Brovko