Caleb Lim created KAFKA-7346:
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Summary: Cannot run Kafka Connect within a web application
Key: KAFKA-7346
URL: https://issues.apache.org/jira/browse/KAFKA-7346
Project: Kafka
Issue Type: Improvement
Components: KafkaConnect
Affects Versions: 1.1.1
Reporter: Caleb Lim
The Plugins class loads plugins using DelegatingClassLoader whose parent class
loader is Application class loader.
public DelegatingClassLoader(List<String> pluginPaths) {
this(pluginPaths, ClassLoader.getSystemClassLoader()); //-> Application
class loader
}
When running Kafka Connect within tomcat web applications, Plugins#pluginClass
always throws ClassNotFoundException because "pluginClass" is loaded not by
Application class loader but by ParallelWebAppClassLoader.
protected static Class pluginClass(...){
Class<?> klass = loader.loadClass(classOrAlias, false);
if (pluginClass.isAssignableFrom(klass)) { // -> returns false
return (Class<? extends U>) klass;
}
throw new ClassNotFoundException(...);
}
Here is the class loader hierarchy when using JsonConverter:
Converter
-ParallelWebAppClassLoader
- URLClassLoader (parent)
-Launcher$AppClassLoader (parent)
JsonConverter
-PluginClassLoader
-DelegatingClassLoader(parent)
-Launher$AppClassLoader
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