Deployed spring boot jar file to Docker - how to access and change static resources

Question

I'm kinda new to spring and web development as a whole.

My question is:

When you build a spring boot project (using Maven) into jar file and deploy it via Docker, everything is in one jar file. How can you access your resources (css, js, images, html...) if you want to edit something? Like change something in css file or add something to html page. Is it even possible? Or do you have to build a new jar file everytime, when you need to change something (in frontend)? Also, when there are being uploaded some images or other files, where are they stored? This stuff is very confusing for me and i can't find any related books or help at all.

Thanks for help!

Answer 1

when you package any java program it is nothing but a zip file. Based on what kind of package it is, you wither name it as a Jar or War.

Jar == Java archive

War == Web archive

Now, given the fact that jar and war both are essentially a zip archive, it gives you flexibility to extract and modify them just like any other zip file.

On windows, I think softwares like 7zip let you update the jar inline. I have done it multiple times, especially when I wanted to change application.properties alone on cloud machines, and no other code changes were required. In such cases, building the whole jar and transferring it again to cloud machine could be time consuming. So I would just extract the contents, update whatever I want to, and rezip the package.

Here is the commands you can use -

jar xf jar-file

This should extract the files into a directory.

This SO thread will guide you towards creating jar files.

Something like jar cf myJar.jar ** should be enough to generate a jar file IMO, but syntax might vary.

Answer 2

The jar file is actually just a zip file containing all the files and classes of your application, so technically you can change files in it like any other zip archive. Best practice is to build the jar file using Maven or Gradle from source every time you need something changed.

It's good practice to keep the source in version control using Git, and tag each build in the git repository - that way you can easily keep track of changes to the jar file by looking at what's in git at the time of the build.