How create object of ScriptableObject in java-scripts.....?

Question

when I try to make an object of a class in java-script file which extends ScriptableObject... The following error will arise.

js: uncaught JavaScript runtime exception: TypeError: Cannot find default value for object.”

class file is

package sumit2;
import org.mozilla.javascript.ScriptableObject;
public class Sumit extends ScriptableObject {
public String getClassName(){
    return "Sumit";
}   
public void foo() {
    System.out.println("Sumit!!!!!!!");
}
}

Java-Script File is:-

importPackage(Packages.sumit2);
var vv=new Sumit();
print(vv.foo());

hoge1e3 · Accepted Answer · 2011-09-30 03:35:22Z

First, you have to override getDefaultValue in Sumit. This is needed to convert object to string from javascript.

package sumit2;

import org.mozilla.javascript.ScriptableObject;
public class Sumit extends ScriptableObject {
    public String getClassName(){
        return "Sumit";
    }   
    public void foo() {
        System.out.println("Sumit!!!!!!!");
    }
    @Override
    public Object getDefaultValue(Class<?> typeHint) {
        return toString();
    }

}

And then, you will get following error message:

js: uncaught JavaScript runtime exception: TypeError: Cannot find function foo in object sumit2.Sumit@1bf6770.

**NOTE: The exception "Cannot find default value for object.” was caused when displaying exception above. The string value "sumit2.Sumit@1bf6770" is produced by calling getDefaultValue

Second, javascript cannot call java methods of objects extended from ScriptableObject. If you want to call foo from javascript, override get(String, Scriptable) like following:

package sumit2;

import jp.tonyu.js.BuiltinFunc;

import org.mozilla.javascript.Context;
import org.mozilla.javascript.Function;
import org.mozilla.javascript.Scriptable;
import org.mozilla.javascript.ScriptableObject;
public class Sumit extends ScriptableObject {
    public String getClassName(){
        return "Sumit";
    }   
    public void foo() {
        System.out.println("Sumit!!!!!!!");
    }
    @Override
    public Object getDefaultValue(Class<?> typeHint) {
        return toString();
    }

    @Override
    public Object get(String name, Scriptable start) {
        if ("foo".equals(name)) {
            return new Function() {

                @Override
                public Object call(Context cx, Scriptable scope, Scriptable thisObj,
                        Object[] args) {
                    foo();
                    return "Return value of foo";
                }
                /** ...Implement all methods of Function other than call **/

            };
        }
        return super.get(name, start);
    }


}

And you will get:

Sumit!!!!!!!
Return value of foo

I think the part

/** ...Implement all methods of Function other than call **/

is annoying. I recommend to create an adapter class which implements Function and overrides all methods of Function with empty statements.

So shouldn't the jsFunction_ syntax enable to call Java Functions directly from JS without the hassle of the get-Method?

Sid · Accepted Answer · 2013-05-09 18:34:08Z

0

I tried to use the code concept posted by @hoge1e3 but unfortunately it did not work for me with the latest Rhino build (1_7R5pre). However, I was able to create a Java class with methods that were invokable in JavaScript by using the annotations provided by the Rhino framework. In the end, it was actually very simple and straightforward.

As a reference, please see the examples included in the Rhino source provided by Mozilla: https://github.com/mozilla/rhino/tree/master/examples

Example class definition:

//this gives you access to the annotations needed to expose your Java methods and properties to JavaScript
import org.mozilla.javascript.annotations.JSFunction; 

public class Sumit extends ScriptableObject {

    public String getClassName(){
        return "Sumit";
    }   

    @JSFunction
    public void foo() {
        //add in the above annotation and your Java method 'foo' will now be available in JavaScript
        System.out.println("Sumit!!!!!!!");
    }
}

Example of converting the above class from Java to JavaScript:

//Make sure to define your Context and Scope beforehand
ScriptableObject.defineClass(scope, Sumit.class);

answered May 9, 2013 at 18:34

community wiki

Sid

2 Comments

Nati Krisi Over a year ago

what exactly is scope?

Sid Over a year ago

@NatiKrisi The MDN documentation found here: developer.mozilla.org/en/docs/Rhino/Scopes_and_Contexts, explains what a scope is: "A scope is a set of JavaScript objects. Execution of scripts requires a scope for top-level script variable storage as well as a place to find standard objects like Function and Object."

David P. Caldwell · Accepted Answer · 2011-09-27 21:39:55Z

-2

There is a logical error in the code: you are attempting to print a void value: the return value of vv.foo().

If you change the code from what you have from print(vv.foo()) to: vv.foo(), or alternatively change the Java to return the String "Sumit!!!!!!!" and print that, I think what you have will work.

answered Sep 27, 2011 at 21:39

David P. Caldwell

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1 Comment

Sumit Singh Over a year ago

yeah ...i tried it .. but main problem is with object creation...object is not created.it return TypeError: Cannot find default value for object

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