Java Debugging
Note: we have an example of setting up a debugger in IntelliJ, which is available on Linux, OSX, and Windows. We recommend IntelliJ strongly, since our application is a mix of Scala and Java code, and IntelliJ is the best tool we know that will follow code references and correctly handle code-completion in mixed Java and Scala code.
Open your list of run/debug configurations.

open run/debug configurations
Click "Edit configurations".

Click 'edit configurations'.
Add a new configuration

Add a new configuration
of the "remote debug" type.

Use the remote debug option.
The page should prepopulate with most of these options - fill in
8457
for the port.
Fill in the port, 8457, and check the rest of the settings.
First, run
bin/run-dev
to run a debuggable process. You'll know it's debuggable if it prints Listening for transport dt_socket at address: 8457
in the startup logs. Then, click the bug icon to start debugging with your new debug configuration. You should see this: 
Last modified 8mo ago