Debugging a web application with IntelliJ IDEA

Step 1: go to your tomcat dir and run
             sh bin/catalina.sh jpda start
Step 2: find the port number tomcat is running on.
             ps aux |grep tomcat
             For me I got "address=8000"
Step 3:

 Open you project with IntelliJ IDEA, To do the following steps:

1. Create a new Run/Debug configuration (click on the drop down list on the left of the green arrow icon) and "Edit configurations".
2. Click on the '+' (plus) button and create a new "Maven" configuration.
3. Give it a name.
4. change the port number to what you get in Step 2.
5. And you are good to go!

Step 4: just open you application normally. (not in the port number what you get in Step 2, just normal run port number.)