Building the jar

From the project root (where pom.xml lives):

mvn clean package

• clean wipes target/ so you're not shipping stale classes.
• package compiles, runs tests, and produces the jar in target/.

With the maven-shade-plugin configured (see setup page), you'll get target/my-plugin.jar, this is the file the server loads. Without shading you'd get a jar missing any third-party dependencies you added (besides the provided API), which fail silently at runtime with NoClassDefFoundError.

Useful variants:

mvn clean package -DskipTests     # skip test phase for a quick rebuild
mvn -q clean package              # quiet output, only show errors

Where the jar goes

Every Bukkit/Spigot/Paper server has a plugins/ folder next to its own jar and server.properties:

server/
  paper-1.21.jar
  server.properties
  plugins/
    my-plugin.jar   <- goes here

Uploading to a remote server

Option 1, SFTP/SCP (most common for a VPS):

scp target/my-plugin.jar user@your-server-ip:/path/to/server/plugins/

Or with an SFTP GUI client (FileZilla, WinSCP): connect with the same host/user/port your SSH access uses, navigate to plugins/, and drag the jar in.

Option 2, Managed host control panel (common on Pterodactyl-based hosts like most budget Minecraft hosts): use the panel's file manager, open plugins/, and use its upload button. Some panels also support SFTP directly into the same path.

Option 3, rsync, handy if you're iterating quickly and want to skip re-uploading unchanged files:

rsync -avz target/my-plugin.jar user@your-server-ip:/path/to/server/plugins/

Reloading without a full restart

Full restarts are safer, but for quick iteration:

/plugins          # confirm it's loaded
/reload confirm   # Paper requires this confirmation, many devs still avoid /reload
                   # in production since it can leave old listeners registered

Most experienced plugin devs prefer a full stop + restart, or a plugin manager like PlugMan, over vanilla /reload, because /reload doesn't reliably tear down everything the old plugin instance registered.

A quick scripted deploy loop (local test server)

If you run a local test server for development, a small script saves a lot of manual copying:

#!/usr/bin/env bash
set -e
mvn -q clean package
cp target/my-plugin.jar ~/mc-test-server/plugins/
echo "Deployed. Restart or /reload confirm on the test server."

Save as deploy.sh, chmod +x deploy.sh, then ./deploy.sh after every change.

Common build errors

Next: Decompiling a .jar to .java.