How can I debug my Java class in the Designer?

Unfortunately you have to use a tiny special little trick. You have to use remote debugging. To activate remote debugging in the Designer, please open the file Xpert.ivy Designer.ini in the installation directory of the Designer and add the following line at the end of the file:

-agentlib:jdwp=transport=dt_socket,server=y,address=8001,suspend=n

With this additional JVM argument you permit to a remote debugger to connect with the JVM on port 8001 to debug.

After that, restart the Designer. As a second step, please go to Run -> Debug Configurations and create a new Remote Java Application Debugging configuration. In the configuration, choose the project that you want to debug, set the host and the port (localhost and 8001). And now start the fun with clicking on the Debug button. From now on, the break points will suspend the execution of the Java class so that you can quietly debug your code.

On the server:

Since 7.4:

You have to add the line -agentlib:jdwp=transport=dt_socket,server=y,address=8001,suspend=n in [engineDir]/configuratoin/jvm.options

Before 7.4:

You have to add the same line into the entry ivy.vm.additional.options of the ilc file for the server executable. See the chapter Tools Reference/Windows Program Launcher Configuration for more details about ilc files.

Note: This question and answer was originally posted by Heinrich Spreiter on his Xpert.ivy Hacker blog. Henry, many thanks to you for your enthusiastic work.