1) Add Debugging statement to server script
Add following statement to your server start script:
-Xdebug -Xnoagent -Djava.compiler=NONE -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=5005
The statements have to be inserted between java and -jar statement! This is important.
So it should looks like:
java -Xdebug -Xnoagent -Djava.compiler=NONE -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=5005 -Xms512M -Xmx1024M -XX:MaxPermSize=128M -jar spigot.jar
2) Open Debug Configuration in Eclipse
Click on the arrow next to the "Debug" button and select Debug Configurations...
3) Remote Debug Configuration
Click on Remote Java Application and press the Add button on the top.
On the right side you now see the debug configuration. Name your configuration and type 5005 in the Port textfield.
Click Apply and Close.
Note: You can change the port by editing the start script statement and the debug configuration.
4) Restart your server
With restarting your server the "debug server" will be started on port 5005.
5) Set breakpoint and debug
After that your are able to debug your plugin! Just set a breakpoint in the code, press Debug (your server has to be running) and select the new created Debug configuration in Eclipse. Now start minecraft, join your server and play! When you hit the breakpoint you will see the debug view in Eclipse.
Careful: You have to set max-tick-time to a very high value (eg. 60000000) in your server config [spigot.yml]. So the server won't close after a short time at debugging.
The user will be kicked out of the game really fast, because of a timeout! So you have to remember that!
Thanks for reading And start debug your Plugin.