Loading extensions crashes kotlin application

[makiam]

I try to create Kotlin application with pf4j support and found this issue... (This is very similar to issue #297)
Using pf4j 3.6.0
I try to enable support for system extensions and declare extension to DefaultPluginManager

        val manager: PluginManager = object: DefaultPluginManager() {
            override fun createExtensionFinder(): ExtensionFinder {
                val extensionFinder = super.createExtensionFinder() as DefaultExtensionFinder
                extensionFinder.addServiceProviderExtensionFinder() // to activate "HowdyGreeting" extension
                return extensionFinder
            }
        }

than once I start application and try to find my extension

    init {
        val tools: List<Tool> = ArtOfIllusion.manager.getExtensions(Tool::class.java);
        tools.forEach(System.out::println)
    }

I see this output with exception:
23:24:12.307 [main] INFO org.pf4j.DefaultPluginStatusProvider - Enabled plugins: []
23:24:12.307 [main] INFO org.pf4j.DefaultPluginStatusProvider - Disabled plugins: []
23:24:12.307 [main] INFO org.pf4j.DefaultPluginManager - PF4J version 3.6.0 in 'deployment' mode
23:24:12.408 [main] DEBUG org.pf4j.AbstractPluginManager - Lookup plugins in '[plugins]'
23:24:12.408 [main] WARN org.pf4j.AbstractPluginManager - No 'plugins' root
23:24:12.408 [main] INFO org.pf4j.AbstractPluginManager - No plugins
23:24:12.947 [AWT-EventQueue-0] DEBUG org.pf4j.AbstractExtensionFinder - Finding extensions of extension point 'api.Tool'
23:24:12.947 [AWT-EventQueue-0] DEBUG org.pf4j.LegacyExtensionFinder - Reading extensions storages from classpath
23:24:12.947 [AWT-EventQueue-0] DEBUG org.pf4j.LegacyExtensionFinder - Cannot find 'META-INF/extensions.idx'
23:24:12.947 [AWT-EventQueue-0] DEBUG org.pf4j.AbstractExtensionFinder - No extensions found
23:24:12.947 [AWT-EventQueue-0] DEBUG org.pf4j.LegacyExtensionFinder - Reading extensions storages from plugins
23:24:12.947 [AWT-EventQueue-0] DEBUG org.pf4j.AbstractExtensionFinder - Finding extensions of extension point 'api.Tool' for plugin 'null'
23:24:12.947 [AWT-EventQueue-0] DEBUG org.pf4j.AbstractExtensionFinder - No extensions found for extension point 'api.Tool'
23:24:12.947 [AWT-EventQueue-0] DEBUG org.pf4j.AbstractExtensionFinder - Finding extensions of extension point 'api.Tool'
23:24:12.947 [AWT-EventQueue-0] DEBUG org.pf4j.ServiceProviderExtensionFinder - Reading extensions storages from classpath
23:24:12.947 [AWT-EventQueue-0] DEBUG org.pf4j.ServiceProviderExtensionFinder - Read 'file:/C:/Users/MaksK/.gradle/caches/modules-2/files-2.1/ch.qos.logback/logback-classic/1.2.11/4741689214e9d1e8408b206506cbe76d1c6a7d60/logback-classic-1.2.11.jar!/META-INF/services'
23:24:12.978 [AWT-EventQueue-0] DEBUG org.pf4j.ServiceProviderExtensionFinder - Read 'META-INF/services/javax.servlet.ServletContainerInitializer'
23:24:12.978 [AWT-EventQueue-0] DEBUG org.pf4j.ServiceProviderExtensionFinder - Read 'file:/C:/Users/MaksK/.gradle/caches/modules-2/files-2.1/org.pf4j/pf4j/3.6.0/9025adf3f680069bb1b52863c9ec70d341e09b0/pf4j-3.6.0.jar!/META-INF/services/'
23:24:12.978 [AWT-EventQueue-0] DEBUG org.pf4j.ServiceProviderExtensionFinder - Read 'META-INF/services/javax.annotation.processing.Processor'
23:24:12.978 [AWT-EventQueue-0] DEBUG org.pf4j.AbstractExtensionFinder - Found possible 2 extensions:
23:24:12.978 [AWT-EventQueue-0] DEBUG org.pf4j.AbstractExtensionFinder - ch.qos.logback.classic.servlet.LogbackServletContainerInitializer
23:24:12.978 [AWT-EventQueue-0] DEBUG org.pf4j.AbstractExtensionFinder - org.pf4j.processor.ExtensionAnnotationProcessor
23:24:12.978 [AWT-EventQueue-0] DEBUG org.pf4j.ServiceProviderExtensionFinder - Reading extensions storages from plugins
23:24:12.978 [AWT-EventQueue-0] DEBUG org.pf4j.AbstractExtensionFinder - Finding extensions of extension point 'api.Tool' for plugin 'null'
23:24:12.978 [AWT-EventQueue-0] DEBUG org.pf4j.AbstractExtensionFinder - Loading class 'ch.qos.logback.classic.servlet.LogbackServletContainerInitializer' using class loader 'jdk.internal.loader.ClassLoaders$AppClassLoader@5a07e868'
Exception in thread "AWT-EventQueue-0" java.lang.NoClassDefFoundError: javax/servlet/ServletContainerInitializer
at java.base/java.lang.ClassLoader.defineClass1(Native Method)
at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1016)
at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:151)
at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:821)
at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(BuiltinClassLoader.java:719)
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:642)
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:600)
at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
at org.pf4j.AbstractExtensionFinder.find(AbstractExtensionFinder.java:141)
at org.pf4j.AbstractExtensionFinder.find(AbstractExtensionFinder.java:62)
at org.pf4j.DefaultExtensionFinder.find(DefaultExtensionFinder.java:45)
at org.pf4j.AbstractPluginManager.getExtensions(AbstractPluginManager.java:580)
at artofillusion.ToolsMenu.(ToolsMenu.kt:9)
at artofillusion.LayoutWindow.frameInit(LayoutWindow.kt:26)
at java.desktop/javax.swing.JFrame.(JFrame.java:181)
at artofillusion.LayoutWindow.(LayoutWindow.kt:7)
at artofillusion.ArtOfIllusion.init$lambda-0(ArtOfIllusion.kt:14)
at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:313)
at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:770)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:740)
at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
Caused by: java.lang.ClassNotFoundException: javax.servlet.ServletContainerInitializer
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:602)
at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
... 31 more

Process finished with exit code 0

[decebals]

I think that it's not a problem related Kotlin, it's a missing dependency. Please try to create a Java (preferably vanilla Java) quickstart that replicates your problem.

[makiam]

I found that this issue is definitely not related to Kotlin. I reproduce this issue with vanilla Java code as well. However I think this still may be an issue inside AbstractExtensionFinder code. As I see fix in #297 commit You added extra catch for NoClassDefFoundError for List find(String pluginId) method but in my code I exception thrown from List<ExtensionWrapper> find(Class type, String pluginId) method

[decebals]

@makiam can you share the unit test or the quickstart project that you created to reproduce the issue using vanilla Java code?

[makiam]

JGLApp.zip

[decebals]

So, in your case is not necessary to create an instance of DefaultPluginManager with enabled support for ServiceProviderExtensionFinder (this is necessary when your application contains extensions declared via Java Service Provider mechanism - using META-INF/services)
With this occasion I fixed a bug related to ServiceProviderExtensionFinder. Things on this topic are not very clear because the application can contains multiple dependencies and each dependency could have a META-INF/services. In this case all these services are detected by PF4J as extensions. It's not completely wrong but in same cases I don't want this behavior (I want somehow only my extensions declared via Java Service Provider mechanism).