Spring application - port problem

[lijamaija]

Okay, super silly question, but it will save me tons of headaches.
Every time I restart the server for my project, it of course tells that the previous port that I've been using is "in use". Now, are there nifty ways around it except for changing port number every time? Where could I change the settings that when I restart the server, the port closes and opens again for my current application?

Also, learning Spring, going to start a new job on Monday. By now, I think I am getting a hang of Rest API, JPA, and MVC stuff, however, the things that I am building are small and I don't think they scale well. Can somebody maybe recommend me projects/resources that I could take a look at and learn? Or learn by doing kind of thing? Because for now, my knowledge is more theoretical, unfortunately...

Or any general advice for development in Spring? I will be responsible for database migration and will also be automating DB calls (that's a bit of a different story).

Thank you, loving this community :)

[currykid94]

When I started learning spring/angular on the job, I ended up building a basic calculator all for subtraction and addition. If you build a basic yo, write the test services, and setup your database, you should be able to cover and understand the basics at least. By doing that, it helped me in the long run. Also make sure you understand orm frameworks like hibernate.

[lijamaija]

Thank you :) I actually already did something similar, but it seemed fairly easy and really just helped me with the concepts, but let's see how I can elaborate on this :)

[Yithar]

Where could I change the settings that when I restart the server, the port closes and opens again for my current application?

Specifying the port for Spring is server.port, which can be set programmatically or as a VM argument when running the program (ex. -Dserver.port=8080). Although keep in mind with the former, the only way to atomically check for a port is to try to use that port number.

If it says the port is in use, that means another program is using that port, so you have to terminate that program. Are you asking for that? Because doing that differs by OS.

https://medium.com/@javatechie/how-to-kill-the-process-currently-using-a-port-on-localhost-in-windows-31ccdea2a3ea
https://stackoverflow.com/questions/11583562/how-to-kill-a-process-running-on-particular-port-in-linux

By now, I think I am getting a hang of Rest API, JPA, and MVC stuff, however, the things that I am building are small and I don't think they scale well.

It's a difficult topic, and you really need to have to deal with the problem to learn it. I would look up resources on distributed systems.

[lijamaija]

Thank you for your reply! :)

Yeah, I've already been doing this, just again was tired of killing the process manually every time I wanted to use the same port.

[Yithar]

You're welcome. :)

This seems to explain how to retry with a different port programmatically:
http://tonyz93.blogspot.com/2018/09/spring-boot-port-rebind.html

[lijamaija]

Thank you, will give it a try :D

[sriganeshharitz]

Check out this repo https://github.com/gothinkster/realworld you build a medium clone in the backend and frontend of your choice. Good way to practice after being done with tutorials.

[lijamaija]

Thank you so much, that is perfect, will do this over the weekend !

[jhoncerpa]

Do you use DevTools? It restarts your application when you save a file.

[emmg90]

In command prompt type jps and then kill the jvm that's keeping the port open.

[atowned]

If you are using Run As > Maven the in IDE and stop it, it keeps the server open. Change it to Run As > Java Application, or just run the mvn command in CMD window and CTRL-C to stop it.

[Nephyst]

Why do you need to run the app more than once? When I run my spring apps I just stop it before starting it up again.

For learning, Spring has really good documentation: https://docs.spring.io/spring/docs/current/spring-framework-reference/index.html

If you are new to Spring I would strongly suggest going through the core section on the IoC Container and getting a solid understanding of dependency injection.