javascript - How create object of ScriptableObject in java-scripts.....? - Stack Overflow

admin管理员组

文章数量:1313001

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());

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());

• java
• javascript
• rhino

Share Improve this question Follow edited Jun 20, 2012 at 13:05 Sumit Singh asked Sep 27, 2011 at 10:55 Sumit SinghSumit Singh 15.9k66 gold badges6262 silver badges9090 bronze badges 0

Add a ment  | 

3 Answers 3

Sorted by: Reset to default 9

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 remend to create an adapter class which implements Function and overrides all methods of Function with empty statements.

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./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);

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.

本文标签： javascriptHow create object of ScriptableObject in javascriptsStack Overflow