Execute compiled groovy script from java via reflection

Question

I have many groovy scripts which are compiled with GMaven (located in src/main/groovy/somepackage), each script has run(String, String) function and does not have a class:

// script1.groovy
def run(String name, String arg) {
  // body
}


// script2.groovy
def run(String name, String arg) {
  // body
}

I can find them with Reflections library and resolve their types:

final Set<String> scripts = new Reflections(
  "somepackage",
   new SubTypesScanner(false)
).getAllTypes();
for (String script : scripts) {
  run(Class.forName(name));
}

then I have some issues with execution: I can't create scipt instance because it doesn't have public constructor (has only private one with groovy.lang.Reference parameters) and I can't find run method in this type.

The question: how to execute compiled groovy script (with single method and without a class) from Java using reflection properly?

Szymon Stepniak · Accepted Answer · 2018-04-19 08:37:39Z

You can load compiled Groovy scripts from given package using:

Reflections.getSubTypesOf(groovy.lang.Script.class)

It returns a Set<Class<? extends Script>> so you can iterate over those classes, instantiate them and invoke method using Class.invokeMethod(String name, Object args)

ATTENTION: you wont be able to call this method like script.run(string1, string2), because this method does not exist in parent groovy.lang.Script class.

Below you can find an example:

import groovy.lang.Script;
import org.reflections.Reflections;
import org.reflections.scanners.SubTypesScanner;

import java.util.Set;

public class LoadGroovyScriptExample {

    public static void main(String[] args) throws IllegalAccessException, InstantiationException {
        Set<Class<? extends Script>> scripts = new Reflections("somepackage", new SubTypesScanner(false))
                .getSubTypesOf(Script.class);

        for (Class<? extends Script> script : scripts) {
            script.newInstance().invokeMethod("run", new Object[] { "test", "123" });
        }
    }
}

somepackage/script1.groovy

package somepackage

def run(String name, String arg) {
    println "running script1.groovy: ${name}, ${arg}"
}

somepackage/script2.groovy

package somepackage

def run(String name, String arg) {
    println "running script2.groovy: ${name}, ${arg}"
}

Console output

[main] INFO org.reflections.Reflections - Reflections took 93 ms to scan 1 urls, producing 1 keys and 2 values 
running script2.groovy: test, 123
running script1.groovy: test, 123

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