How to start learning back-end development in Java?

Question

Java

I have been developing android applications for about a year, and I have encountered such a problem that you cannot write normal, useful applications without a server part.
Goal: learn how to write server applications for your android applications
What we have: knowledge of Java core and superficial knowledge of how the client-server architecture works.
I read a lot on the Internet about what to write the server part on, I thought that it makes no sense to learn php or the same node.js, since I already have basic knowledge of java. As far as I understand, you can write full-fledged server applications in java. Again, as far as I understand what exactly java ee is needed to write the server side. But these are my guesses. In general, I think my goal is clear to you. I want to learn how to write a server part in java from scratch. Tell me where to start, what to read or some resources. I would like a resource that will teach you how to write a backend from scratch. If I misunderstood something, please correct me.
PS I ask you not to answer with abstruse words. Sometimes I read answers to other people's questions. So it seems that those who answer do not want to help a person figure it out, but compete among themselves who will give a more abstruse answer.

Answer 1

1. Read about java ee, make simple examples to understand how it works and works. Read about REST.
2. Choose between Spring (Core, MVC, Boot, Data, Security) with its many frameworks and Play. Personally, I did not work with Play.
3. Resources - Documentation is the best resource. There is also https://www.mkyong.com/ + further to Google. Dofigischa resources can be found + search on the toaster, there have already been similar questions, the pack is straight.

Answer 2

The most primitive option is Spark
Then you can watch Play , which is also very simple.
Then Spring.

Answer 3

Try vert.x

Answer 4

Good afternoon, if we consider the server part in Java, then we can dig towards EJB technology (part of Java EE). In fact, these are Java classes on the server that process requests from clients and they implement all the business logic (middle level, application server). As a server, for example, JBoss can be, more precisely now WildFly ( https://ru.wikipedia.org/wiki/WildFly ). In my experience, everything works well, including with Android clients ( www.volocktech.ru/index.php/2016/11/16/javaee-meet...). WildFly can expose both pure Java beans and Web services with WSDL and REST services. We use all of these options. Moreover, Android connects to the server via REST. The main beans with business logic are @Stateless, we use Hibernate (built into WildFly) and PostgreSQL to work with the database. Database operations are performed using plain Java objects with the @Entity annotation.
POJOs are used to exchange with clients (simple Java classes, but not the same as @Entity!)
Using this technology is not a very easy way, but it is a good option for creating serious applications.
If you want to study the technology properly, it is better to have a book like this: https://www.litres.ru/debu-panda-2/ejb-3-v-deystvi...
There are even simpler options for Servlet technology, but I won’t say anything about them, because. did not use.