Ninja is based around standards. If you run a Ninja application inside a servlet container you can simply connect to the servlet container via your IDE and debug the running application. So there are potentially a lot of ways how you can debug your app.
Feel free to suggest other ways to debug a Ninja application!
Our favorite way to debug an application is to use Eclipse. We are always using the m2eclipse plugin to import our project.
And if you make a left click on your project you get the option “Debug as…”. Hit that and generate a profile that debugs the goal jetty:run. That’s all. Now Eclipse starts your application and you can cleanly debug everything that is going on.
The Ninja maven plugin supports
-Dninja.jvmArgs as a property that allows any
arbitrary values to passthru to the forked Ninja JVM. You have the option of passing
thru the required JVM properties to enable debugging.