Web server in Java for a mobile application, where to dig?

Question

Java

Good day!
I dug through three tons of pages on Habré, on the Internet and in books, but because of the abundance of information, the advice of experienced people is required. So, experienced, dedicated to you.
The idea is simple - a mobile application (iOS), with a web server (glassfish servlets) and a database (postgreSQl). My area of ​​expertise includes an intermediate point, a web server.
I use Eclipse as an IDE, I successfully deployed simple servlets on glassfish, but now we need to receive user data (login / password) from the mobile application, check for the presence of this in the database, and if there are such, return a positive response!
And now, questions!
As far as I understand, you need to create a listner in the package (listening to some port), which will grab data from the application, then apparently do a search in the database (do I need to bind it to glassfish?), And actually - that's it?
The sadness is that I don’t really understand in the sea of ​​​​information where to read a normal guide. Can you recommend a book or take one given? With midi-chlorians in the blood, everything is fine, there is power!

Answer 1

The best solution would be to use a RESTful web service to check if the user exists in the database.
RESTful API for the server