One of the worst things to debug can be something that works just fine in your local development environment but does not work in a deployed environment. If you deploy to Tomcat, you can debug it remotely. If you use IntelliJ IDEA, you can do it with style.
IntelliJ makes it easy. First, you want to click the runnable configurations dropdown and select "Edit Configurations":
Once in the "Edit Configurations" dialog, click the "+" Plus icon to create a new configuration. Select "Remote":
This dialog is the last, and you will need to configure your connection:
Host: Either IP or hostname of remote server
Port: Must match debug port opened on remote Tomcat (address arg below)
As is explained to you on the window, you need to be able to add JVM arguments to the remote JVM. By now, let us hope that we're all using a JDK more recent than JDK 1.3. :) In that case, you'll need:
To get those args on the server might require different mechanisms by default. My environment's deploy is automated to put the args on the JAVA_OPTS variable in:
But if your deployment doesn't apply JVM properties for your app, you can put them in:
export JAVA_OPTS="-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=7007"
Finally, restart the remote server, and your debugging port will be open. Start your remote connection in IntelliJ and set a break point. Exercise your deployed app so your code will be executed, and let the good times roll!