How to invoke Rhino compiled JavaScript methods (class files) in the Java program?

Question

I compiled following JavaScript file, "test.js", into the "test.class" :

var test = (function () {
  var that = {};

  that.addNumbers = function (a, b) {
    return a+b;
  };

  return that;
}());

I would like to call the compiled JavaScript function, "test.addNumbers(1,2)", in the simple Java program "run.java" as follows :

public class run {

  public static void main(String[] args) throws Exception {

    Context cx = Context.enter();
    
    try {
      Scriptable scope = cx.initStandardObjects();
    
      // HOW TO CALL THE METHOD, Test.addNumbers(1,2)?  Please help me!
        
    } finally {
      Context.exit();
    }
  }
}

I tried many ways, but failed. I read Rhino tutorial and examined many articles and examples, BUT they only show how to call JavaScript methods from the command line or the source file, "test.js". I need to call the method from the compiled "test.class" file.

McDowell · Accepted Answer · 2011-02-20 13:27:47Z

5

Using javap, I believe that the JavaScript type test does not mean that the resultant Java type is this class. The generated Java type invokes the script code in its constructor; this will not result in exposing addNumbers as a Java method.

>javap -classpath . test
public class test extends org.mozilla.javascript.NativeFunction implements org.m
ozilla.javascript.Script{
    public test(org.mozilla.javascript.Scriptable, org.mozilla.javascript.Contex
t, int);
    public test();
    public static void main(java.lang.String[]);
    public final java.lang.Object exec(org.mozilla.javascript.Context, org.mozil
la.javascript.Scriptable);
    public final java.lang.Object call(org.mozilla.javascript.Context, org.mozil
la.javascript.Scriptable, org.mozilla.javascript.Scriptable, java.lang.Object[])
;
    public int getLanguageVersion();
    public java.lang.String getFunctionName();
    public int getParamCount();
    public int getParamAndVarCount();
    public java.lang.String getParamOrVarName(int);
    public java.lang.String getEncodedSource();
    public boolean getParamOrVarConst(int);
}

Reading between the lines, I'd say you need to map to Java types to do what you want. From the jsc doc:

-implements java-intf-name

Specifies that a java class implementing the Java interface java-intf-name should be generated from the incoming JavaScript source file. Each global function in the source file is made a method of the generated class, implementing any methods in the interface by the same name.

Define this interface:

//Adder.java
public interface Adder {
  public int addNumbers(int a, int b);
}

Write this implementation:

//AdderImpl.js
function addNumbers(a, b) {
  return a+b;
}

Compile the JavaScript with the arguments -implements Adder AdderImpl.js. Invoke the method like so:

Adder adder = new AdderImpl();
int n = adder.addNumbers(1, 2);
System.out.println(n);

I'd hazard a guess that it was probably necessary to do it this way because of differences in the languages' type systems.

I used Rhino 1.7R2. For the sake of brevity, I've avoided using packages, etc.

answered Feb 20, 2011 at 13:27

McDowell

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2 Comments

Haesung Over a year ago

Thank you very much for your help, it works! I dont need to worry about preparing Context things, instead "new" on the implementation class and just use the interface methods. Fantastic!

TheRealChx101 Over a year ago

Now, what if you want to add class shutters to the final compiled code.

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