In the following test, a JavaScript function is called from Java program.

import javax.script.*;

public class Test {
    public static void main(String[] argv) throws Exception {
        ScriptEngineManager manager = new ScriptEngineManager();
        ScriptEngine engine = manager.getEngineByName("js");

        // function expects a java.io.File object.
        engine.eval(
           "function func(obj) { " +
           " if (!(obj instanceof java.io.File)) { " +
           " throw 'file expected'; " +
           " } else { " +
           " print('got : ' + obj); " +
           " } " +
           "} ");

        Invocable in = (Invocable) engine;
        // call the func by passing a java.io.File object
        // we don't expect exception because we are passing right
        // type of object as argument...
        in.invoke("func", new Object[] { new java.io.File(".") });
    }
}


We don't expect any exception in the above program. But, we get exception with the following trace:

Exception in thread "main" javax.script.ScriptException: sun.org.mozilla.javascript.internal.JavaScriptException: file expected (<Unknown source>#1) in <Unknown source> at line number 1
        at com.sun.script.javascript.RhinoScriptEngine.invoke(RhinoScriptEngine.java:204)
        at com.sun.script.javascript.RhinoScriptEngine.invoke(RhinoScriptEngine.java:156)
        at Test.main(Test.java:20)

It seems that the arguments passed to script function are not converted to correct script wrapper objects.