can I debug the java project built by gradlew using IntelliJ IDEA ?

Do you want to debug the application, launched by gradel task or you want to debug a Gradle task itself?

How do you launch the Gradle task exactly?

The requirement to be able to debug - is to launch the java process which you want to debug with java debug options

https://www.baeldung.com/java-application-remote-debugging#launch-command

https://stackoverflow.com/questions/975271/remote-debugging-a-java-application

and then attach to this process. To attach to a process you can use Java remote debug configuration.