Java 5, 6, 7 and newer

The Java™ Platform Debugger Architecture (JPDA) supports certain JVM invocation options.

Usually this boils down to:

-agentlib:jdwp=transport=dt_socket,server=y,suspend=y

This will cause your JVM process to execute but wait (suspend=y) and listen for a socket connection from a remote debugging client on a free port (which it will write to stdout. The suspend=y option is especially useful if you need to debug code that runs during the start-up phase of your application.

If you don’t want the process to do the initial waiting, then use suspend=n.

Java 1.4

If you are for some terrible reason stuck on Java 1.4, then you must use the older approach like this:

-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n

Tomcat

To enabled remote debugging for a Apache Tomcat on Windows, create bin\setenv.bat in your Tomcat installation, with this content:

set "CATALINA_OPTS=-agentlib:jdwp=transport=dt_socket,server=y,suspend=n"

Network port

If you use the settings above, i.e. server=y and no “address” option, JPDA will pick a free port and write a message about this to stdout. Look for something like this:

Listening for transport dt_socket at address: [PORT]

Intellij configuration

Add a debug configuration via Run menu: