ASTArrayAccess messes up on fallback to JexlContext
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Key: JEXL-26
URL: http://issues.apache.org/jira/browse/JEXL-26
Project: Commons JEXL
Issue Type: Bug
Affects Versions: 1.1
Environment: N/A
Reporter: Colin Lear
When executing an expression if a null comes up (unresolved object) it attempts
to build an identifier to query the JexlContext directly. However it only works
on sequential ASTIdentifier nodes. If there is another sort of node then it
ends up searching the JexlContext for a mangled or malformed variable.
I think this is a bug because subobjects with properties or methods that are
null can "inherit" the value of objects or properties in the base JexlContext
scope. It's too unpredictable to be a legitimate feature.
for example in the expression: objects[23].status
if (objects[23] != null && objects[23].status == null) then it will search for
the bare expression "status" in the JexlContext. Ideally it would query the
JexlContext map for the full expression, however the details of that are
difficult to implement and can produce odd results.
Even worse with an expression like: base.objects[23].status.
if (base != null && base.objects[23] != null && base.objects[23].status ==
null) then this expression will evaluate look for "base.status" in the
JexlContext map.
It currently works as expected for expressions like base.object.status by
searching for "base.object.status" in the JexlContext if status is null.
Although I'm not entirely convinced that it is a good idea to do this.
Simple Fix:
in ASTReference.java change the function getIdentifierToDepth() to return an
empty string if there are non ASTIdentifier Nodes in the expression (in my case
it's ASTArrayAccess nodes). This is the simplest solution and stops subobjects
effectively assuming values of objects in the base JexlContext while still
allowing you to bind objects into the JexlContext with identifiers with "." in
the name.
So you could add "object.tracking.status" directly into the JexlContext and it
would work. However you couldn't add object.tracking[23].status because one of
the Nodes is an ArrayAccess node and it can't be translated back into a string
by the current implementation.
/* patched function */
private String getIdentifierToDepth(int i) {
StringBuffer varName = new StringBuffer();
for (int j = 0; j <= i; j++) {
SimpleNode node = (SimpleNode) jjtGetChild(j);
if (node instanceof ASTIdentifier) {
varName.append(((ASTIdentifier) node).getIdentifierString());
if (j != i) {
varName.append('.');
}
} else {
/* expression is unresolvable and variable name is invalid */
return "";
}
}
return varName.toString();
}
You could always add some code to support ASTArrayAccess nodes. However you'd
also have to support either evaluating, or reducing to a string, the index
expression. Which is messy.
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