Subj : Re: Sealing Scopes
To   : vige46
From : Igor Bukanov
Date : Fri Oct 08 2004 12:40 am

Miro wrote:
> Hi, 
> 
> I'd like to use one top ScriptableObject among several threads as
> described in http://www.mozilla.org/rhino/scopes.html
> I'd like to combine it with sealing the top scriptable object: 
> 
> <pre>
>       Context tempContext=Context.enter();
>       sharedScope=new ImporterTopLevel(tempContext,true);
>       //BLOCK1: ....some operations:
>       tempContext.evaluateString(sharedScope,"importPackage(Packages.java.util);",null,0,null);
>       sharedScope.put("a",sharedScope,new Integer(10));
>       //seal object then
>       sharedScope.sealObject();
>       Context.exit();
> </pre>
> 
> In another thread, I'd like to use this sharedScope as a prototype for
> another( local) scope:
> 
> <pre>
>         Context context;
>         context=Context.enter();
>         
>         Scriptable scope=new ImporterTopLevel(context,true);
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> 
>         scope.setPrototype(sharedScope);
>         scope.setParentScope(null);
> </pre>
> 
> Everything works fine( I have access to propertie 'a' defined in
> BLOCK1), untill I execute JavaScript command, which defines new
> property
> 
> <pre>
>         Object returnValue=context.evaluateString(scope, "var l = new
> LinkedList();", null, 0, null);
> </pre>
> 
> When calling this, I get org.mozilla.javascript.EvaluatorException:
> Cannot remove a property from a sealed object: XML.


The underlined line creates a sealed object containing another copy of 
the standard objects. If you replace that by
          Scriptable scope = cx.newObject(sharedScope);

then it should work.

Also you have to always use the pattern:

contextInstance = Context.enter();
try {
....
} finally {
     Context.exit();
}

or you get a resource leak.

Regards, Igor

.