How to use import inside a dynamically loaded groovy file - groovy

Question

I am trying to come up with a way for my users to supply plugins into the main groovy application by dynamically loading their source file. But their groovy file contains import statements and I don't know how to make them work even with an apparently good classpath.
The main application is a shell script, bin/top.sh:
#!/bin/bash
groovy-2.4.1/bin/groovy -cp lib lib/Top.groovy
The lib/Top.groovy class:
public class Top {
public static void main(String[] args) {
ClassLoader parent = getClass().getClassLoader()
GroovyClassLoader loader = new GroovyClassLoader(parent)
Class groovyClass = loader.parseClass(new File("UserPlugin.groovy"))
GroovyObject groovyObject = (GroovyObject) groovyClass.newInstance()
groovyObject.invokeMethod("run",args)
}
}
The user class UserPlugin.groovy:
// The following import can be found in the classpath
// passed by the shell script (under lib/, next to Top.groovy)
import Lib
class UserPlugin {
def UserPlugin() {
Lib lib = new Lib()
}
def run(String [] args) {
println("Running with: "+args)
}
}
And the lib/Lib.groovy:
class Lib {
def Lib() {
println("Lib")
}
}
When I run with bin/top.sh, I get: UserPlugin.groovy: 3: unable to resolve class Lib
When I add lib to the class loader like so loader.addClasspath('lib'), it's rather catastrophic:
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
General error during class generation: java.lang.NoClassDefFoundError: groovy/lang/GroovyObject
java.lang.RuntimeException: java.lang.NoClassDefFoundError: groovy/lang/GroovyObject
at org.codehaus.groovy.control.CompilationUnit.convertUncaughtExceptionToCompilationError(CompilationUnit.java:1088)
How can this work while keeping it all scripted and not compiled? Is this even possible?

Answer 1

Sorry I don't have time to find the bug but I think the problem is with the setting of the context classloader. GroovyShell.run takes care of that for you which I recommend over replicating that code.
Top.groovy
public class Top {
public static void main(String[] args) {
new GroovyShell().run(new File("UserPlugin.groovy"), args)
}
}
If you're willing to make Top.groovy a script rather than class then you can do this:
Top.groovy
run(new File("UserPlugin.groovy"), args)
The UserPlugin.groovy then needs to be either a class (with a main method) or a script to use the standard Groovy calling logic.