Hi Pete,
On Tue, 2004-01-13 at 16:41, peter royal wrote:
> lets leverage the map! the map knows if a variable exists. So how about
> JexlExpression.setExplicitVariableDeclaration( true ); and then Jexl
> just does (in ASTIdentifier, and I think that might be the only
> place..)
That would work. My only argument against it is that if someone adds
another usage for JexlContext.getVars().get() then they might forget to
add that check. So it's a maintenance issue.
To be honest, I don't understand what ASTIdentifier does (not that it is
opaque, just that I haven't explored yet). All I know is that there are
41 other implementations of SimpleNode.value().
(Yet) another solution:
Get the JexlContext to track which variables it was asked for. Note
which ones were known and which were not known. Then you can ask
JexlContext for the list at the end.
It's good because it doesn't break the API and it doesn't mean delving
into Jexl to find all the places that it needs to be done in.
It's not thread-safe. But, we can clone a JexlContext easily enough. How
about:
Expression.check(JexlContext);
And the implementation looks *something* like:
public String[] check(JexlContext context) {
// Clone the context
CheckingContext checkingContext = new CheckingContext(context);
// Evaluate as normal
evaluate(checkingContext);
// Return the list of unknown variables
return checkingContext.getUnknownVariables();
}
Well, we can't be accused of being short of ideas! Not sure of the
performance problems here - but I think, like XML parsing, people are
happy to accept that if they want to be strict.
- Bill
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