A GroovyClassLoader that gathers up the bytecode that defines the classes it has compiled.

GatherClassBytecode.groovy

import org.codehaus.groovy.ast.ClassNode
import org.codehaus.groovy.control.CompilationUnit
import org.codehaus.groovy.control.SourceUnit

class MyGroovyClassLoader extends GroovyClassLoader {
    MyGroovyClassLoader(ClassLoader parent) { super(parent) }
    Map bytecodes = [:]

    class MyClassCollector extends GroovyClassLoader.ClassCollector {
        protected MyClassCollector(GroovyClassLoader.InnerLoader cl, CompilationUnit unit, SourceUnit su) {
            super(cl, unit, su)
        }

        @Override
        protected Class createClass(byte[] code, ClassNode classNode) {
            bytecodes[classNode.name] = code
            super.createClass(code, classNode)
        }
    }

    @Override
    protected GroovyClassLoader.ClassCollector createCollector(CompilationUnit unit, SourceUnit su) {
        new MyClassCollector(new GroovyClassLoader.InnerLoader(this), unit, su)
    }
}

def loader = new MyGroovyClassLoader(this.class.classLoader)
def scriptClassName = 'ScriptNameToLookFor'

// Compile via GroovyClassLoader:
// def script = loader.parseClass('println \'Hello\'', scriptClassName + '.groovy')

// Or go through GroovyShell:
def shell = new GroovyShell()
shell.loader = loader // Work around borked API/implementation
def script = shell.parse('println \'Hello\'', scriptClassName + '.groovy')

println loader.bytecodes.collectEntries { k, v -> [k, v.length] }
// ==>
// [ScriptNameToLookFor:6010]