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https://issues.apache.org/jira/browse/JEXL-228?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16062955#comment-16062955
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Henri Biestro commented on JEXL-228:
------------------------------------
There should be a way to preserve standard behavior by creating a new
ResolverStrategy & PropertyResolver.
see
http://commons.apache.org/proper/commons-jexl/apidocs/org/apache/commons/jexl3/introspection/JexlUberspect.ResolverStrategy.html
> Ability to read j.u.Collection elements other than instanceof j.u.List by
> using [] and . operator
> -------------------------------------------------------------------------------------------------
>
> Key: JEXL-228
> URL: https://issues.apache.org/jira/browse/JEXL-228
> Project: Commons JEXL
> Issue Type: Improvement
> Affects Versions: 3.1
> Reporter: Dmitri Blinov
> Priority: Minor
>
> In the current implementation of Jexl there is a possibility to address in a
> script the specific elements of {{List}} and {{Array}} by using operators
> {{[]}} or {{.}}, whereas its not that simple for descendants of {{Set}} or
> any other {{Collection}} descendant, as there is no such an operator for them
> out of the box. But in practice this is not so uncommon task for a script
> writer to get, for example, the first element of the LinkedHashSet, which is
> supposed to maintain the logical order of its elements, but unfortunately
> does not implement {{List}} interface for us to be able to address its
> elements in that order. I believe such a basic functionality - deserves to be
> available for script witers from the start.
> I have been experimenting with overloading access operators in customized
> JexlArithmetic for a while and have managed to overload operators {{[]}} and
> {{.}} so that they could be used not only for {{List}} interfaces but for
> other {{Collection}} types as well:
> {code}
> protected Object nth(Collection c, int i) {
> if (c instanceof List) {
> List list = (List) c;
> return list.get(i);
> } else {
> for (Object o : c) {
> if (i-- == 0)
> return o;
> }
> }
> return null;
> }
> public Object propertyGet(Collection c, Number n) {
> return nth(c, n.intValue());
> }
> public Object arrayGet(Collection c, Number n) {
> return nth(c, n.intValue());
> }
> {code}
> But I'm not satisfied with the fact that I have disabled alltogether the
> initial Jexl implementation of access operators for {{LIst}} types.
> The suggestion is to add the ability for Jexl scripts to read, not
> manipulate, elements of any {{Collection}} type.
> BTW, I have found that for {{List}} elements this solution is roughly 50%
> faster compared with that of built-in Jexl List access implementation, so may
> be there should be a place for a performance improvement in a way Jexl itself
> accesses list elements.
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