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External Modules

External modules load JavaScript source from files or byte streams.

File Module

script.getModuleManager().addModule(
    new SimpleScriptFileExternalModule("external", Path.of("external.mjs"))
);

If the path is a directory, SimpleScriptFileExternalModule loads index.mjs by default.

Custom entry point:

new SimpleScriptFileExternalModule("external", Path.of("scripts"), "main.mjs");

Stream Module

script.getModuleManager().addModule(
    new SimpleScriptStreamExternalModule(
        "dynamic",
        "dynamic.mjs",
        "export const value = 10;".getBytes(StandardCharsets.UTF_8)
    )
);

Supplier-based modules reload bytes on every load:

new SimpleScriptStreamExternalModule("dynamic", "dynamic.mjs", () -> loadBytes());

GraalVM Behavior

GraalVM uses VirtualModuleFileSystem.

Behavior:

  • internal modules are generated as virtual JavaScript module source;
  • file external modules are resolved to real files after path security checks;
  • stream external modules are loaded into virtual channels;
  • scripts are evaluated as JavaScript modules.

Supported JavaScript:

import { value } from "external";

Rhino Behavior

Rhino loads source bytes and transforms supported imports/exports.

Supported import forms:

import * as name from "module";
import { value, other as alias } from "module";
import defaultValue from "module";
import "module";

Supported export forms:

export { value, internalName as publicName };
export const value = 1;
export let value = 1;
export var value = 1;
export function name() { }
export class Name { }
export default expression;

Rhino transformation is not a full JavaScript parser. Keep import/export declarations top-level and normally formatted.

Security

File modules should be used with securityMode enabled when scripts or module paths are not fully trusted.

script.getSecurityManager().setSecurityMode(true);
script.getSecurityManager().addExclude(SecurityExclude.ofPath("scripts"));