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Access control in BeanShell classes and methods

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Access control in BeanShell classes and methods

Pascal Meheut
Hi, this is my first post in this list and I hope it is appropriate. If
not, let me know.

I'm trying to integrate BeanShell in a commercial software not only to
provide scripting but also to support dynamically created methods in
also dynamically created classes.
For the dynamically created classes, we generate the bytecode and load
ourself for various reason, mainly easy integration in our screen &
persistence system.

But on top of normal, stored attributes in these classes, I would like
to support some formulas too. Basically, the idea is to allow a
power-user to add its own types in the system and stuff like "field
c=field a+field b"... Nothing new but helps a lot to make a commercial
system more flexible.

Instead of parsing and compiling/interpreting the formulas myself, I
would like to use BeanShell of course. But a lot of access control comes
in the way.
Here are a few examples:

- I want to check in realtime if the formula the user enters is valid.
To do so, the system calls a method like this:

    public LabeledBoolean checkFormula()
    {
      if(formula!=null && formula.length()>0)
      {
        Parser parser=new Parser(new StringReader(formula));
        try
        {
          parser.Expression();
        }
        catch (ParseException exception)
        {
          return new LabeledBoolean(false, exception.getMessage());
        }
      }
      return LabeledBoolean.OK;
    }

and display the results near the formula field on the screen. But if I
want to check more things, for instance the syntaxic tree out of the
parser to detect any BSHAmbiguousName and checks its name against the
valid ones, i.e. the ones declared in my dynamic class, I can't.
Because even SimpleNode is package protected, not public.

Isnt'it strange that "popNode" is public but returns a package-only class ?


- I find also difficult to remove the default imports. For instance, I
do not want the scripts in the system to access Swing. I can of course
give my own namespace and detect such access but the simplest solution
would be to extends NameSpace and to override loadDefaultImports.
But even if I do so, I cannot easily put this MyNameSpace as the global
one.
Because the interpreter constructor does:

        BshClassManager bcm = BshClassManager.createClassManager( this );
        if ( namespace == null )
            this.globalNameSpace = new NameSpace( bcm, "global");

And if I want to pass it MyNameSpace,  it has to be built before and so
cannot contains the link to BshClassManager.createClassManager( this )...
Ok, I know the BshClassManager is not used a lot in NameSpace and I
could pass null but will it still work in the future...

- Same thing for getNameResolver and the names Hashtable? Even if I
found workaround, it would have been nice to have them as protected to
connect the NameSpace to my own objects (importObject is not enough.
Works fine for fields and methods but not for bean properties)

I know that moving something from "package" access to "protected" has a
lot of impact because it becomes part of the contract of the class with
the external world and cannot be changed easily later on without
breaking source code compatibility but in some cases, it would also
extend the useability of BeanShell a lot.

Waiting for your answers and back to coding...

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