This scripts working fine in ADStudio. This is also observed in V16

Refer to this NetBeans issue: Cannot start NetBeans Runtime Container in web app

Here ia my analysis on why ADServer is getting ClassCircularityError:

1. During ADServer/Tomcat startup, it installs a URLStreamHandlerFactory for the java.net.URL class (see org.apache.catalina.loader.WebappLoader#start) The URLStreamHandlerFactory instance is used to construct a stream protocol handler from a protocol name, in this case, the JAR file loading protocol
2. When the user executes a script which refers to NetBeans some functionality (e.g. NetbeansDifferenceLineProcessor), NetBeans startup code registers its own ProxyURLStreamHandlerFactory for the java.net.URL class (it actually forces this registration by using reflection, see org.netbeans.ProxyURLStreamHandlerFactory#register)
3. At this point, the JVM has a org.apache.catalina.loader.WebappLoader, but a org.netbeans.ProxyURLStreamHandlerFactory for the URL class
4. When a new class needs to be loaded later on, WebappLoader tries to create a new URL instance (for the JAR file). The URL constructor then makes a call to ProxyURLStreamHandlerFactory#createURLStreamHandler (recall the factory has been replaced by NetBeans)
5. ProxyURLStreamHandlerFactory#createURLStreamHandler implementation attempts to create a new instance of org.netbeans.JarURLStreamHandler - this invokes item 4 again. The second call to ProxyURLStreamHandlerFactory#createURLStreamHandler triggers a ClassCircularityError

​Once ADServer/Tomcat reached the state described in item 3, no new classes could be loaded further

Is com.aquafold.editor.standalone.api.Bootstrap.bootstrap() called at any point?

Is com.aquafold.editor.standalone.api.Bootstrap.bootstrap() called at any point?

@emil - No. That method was never called. I tried calling it in webapp initialization and that seemed to have fixed the ClassCircularityError problem. I looked the body of that method and found references to the ClassCircularityError problem. So it seems that the only code we need, in the context of an webapp (which doesn't need any editor UI), is the following:

Class.forName("org.netbeans.JarClassLoader$JarURLStreamHandler");

I tried the above only during webapp initialization and it also solved this issue. What are your thoughts of just doing the above?

Yes, as long as you don’t need anything else feel free to just call Class.forName("org.netbeans.JarClassLoader$JarURLStreamHandler");

Verified in 17.0.0-beta-4

@kin-hong: I've re-opened in order to have this fix backported to v16 as well

Verified in ADS 16.0.8 and 17.0.0-beta-4 both.

Verified in ADServer-17.0.0.-GA-21. Refer updated screenshot '2948-ADserver-17-Ga-21.png'

Verified in ADServer-18.0.0-beta-32 . Refer updated screenshot '2948_updated_ADS-v-18.png'