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From "dion gillard (JIRA)" <j...@apache.org>
Subject [jira] Resolved: (JEXL-26) ASTArrayAccess messes up on fallback to JexlContext
Date Sun, 28 Oct 2007 09:08:50 GMT

     [ https://issues.apache.org/jira/browse/JEXL-26?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

dion gillard resolved JEXL-26.
------------------------------

    Resolution: Fixed

This is fixed in the 2.0 branch.
There is a test in ArrayAccessTest.testArrayAndDottedConflict() which makes sure it works
correctly.

> ASTArrayAccess messes up on fallback to JexlContext
> ---------------------------------------------------
>
>                 Key: JEXL-26
>                 URL: https://issues.apache.org/jira/browse/JEXL-26
>             Project: Commons JEXL
>          Issue Type: Bug
>    Affects Versions: 1.1
>         Environment: N/A
>            Reporter: Colin Lear
>             Fix For: 2.0
>
>
> 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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