javaxscriptInvocable

javax.script.Invocable is a Java interface in the javax.script package that extends the scripting framework to allow dynamic invocation of script-defined functions and methods from Java, and to enable scripts to call Java interfaces or methods. It is part of the Java Scripting API (JSR 223) and is implemented by many script engines that support interactive or host-language interoperability, such as JavaScript engines that existed in Java (for example, Nashorn or Rhino in earlier environments).

Core capabilities include:

- invokeFunction(String name, Object... args): calls a top-level function defined in the script by name, returning the result as an Object.

- invokeMethod(Object thiz, String name, Object... args): calls an instance method defined on a script object referred to by thiz, with the given arguments.

- getInterface(Class<T> clasz): creates a proxy that implements the given Java interface, delegating method calls to a script function or object as defined by the engine.

- getInterface(Object thiz, Class<T> clasz): creates a Java interface proxy bound to a script object, enabling typed interaction from Java to a script.

Usage pattern typically involves obtaining a ScriptEngine, ensuring it implements Invocable, and casting to Invocable to perform calls. Example: obtain an engine by name, cast to Invocable, and call invokeFunction("sum", 1, 2, 3). getInterface can be used to adapt a script object to a Java interface for type-safe calls.

Notes:

- Not all script engines implement Invocable; check engine capabilities or use instanceof Invocable before casting.

- The Nashorn engine supported Invocable in Java 8, but Nashorn was removed in later Java releases; other engines (e.g., GraalVM) may provide similar functionality.