Compiling and using Groovy classes from Java at runtime?

Question

I have an app which I'd like to make extensible by letting users define classes in Groovy, eventually implementing some interfaces.

The key aspect is that it should be interpreted/compiled at runtime. I.e. I need my app to take the .groovy and compile it. Doing it during boot is ok.

Then, of course, my app should be able to instantiate that class.

I see two solutions:

1) Compile while the app runs, put the classes somewhere on classpath, and then just load the classes, pretending they were always there.

2) Some smarter way - calling a compiler API and some classloading magic to let my system classloader see them.

How would I do option 2)?
Any other ideas?

Answer 1

Have a look at Integrating Groovy into applications

• Get class Loader
• Load class
• Instantiate class.

Beauty:-
Since .groovy compiles to .class bytecode, parsing the class would give you an instanceof Class. Now it becomes all JAVA world, only difference, once you get hold of GroovyObject after instantiatiation, you play around invoking methods on demand.

Edit: Just so it's contained here:

InputStream groovyClassIS = GroovyCompiler.class
     .getResourceAsStream("/org/jboss/loom/tools/groovy/Foo.groovy");

GroovyClassLoader gcl = new GroovyClassLoader();
Class clazz = gcl.parseClass(groovyClassIS, "SomeClassName.groovy");
Object obj = clazz.newInstance();
IFoo action = (IFoo) obj;
System.out.println( action.foo());

and

package org.jboss.loom.migrators.mail;

import org.jboss.loom.tools.groovy.IFoo;

public class Foo implements IFoo {
    public String foo(){
        return "Foooooooooo Action!";
    }
}