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From "Henri Biestro (JIRA)" <j...@apache.org>
Subject [jira] Commented: (JEXL-97) JEXL parses long expressions with lots of parenthesis slowly
Date Fri, 12 Feb 2010 17:48:28 GMT

    [ https://issues.apache.org/jira/browse/JEXL-97?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12833085#action_12833085
] 

Henri Biestro commented on JEXL-97:
-----------------------------------

There is no "plan" in getting a new 1.1 out AFAIK ; 2.0 is supposed to replace it (hopefully
with some added benefits).
You always have the choice of a local 1.1 fix / release if you are in an emergency situation.

May I suggest you have a closer look at 2.0 and assess how much you miss from 1.1 ? The jexl-compat
lib might give you a quick evaluation path.

If you can elaborate what you mean by "too much tied into it" in a post to the mailing list,
you'll most likely get advice/help on migrating/reimplementing features .

> JEXL parses long expressions with lots of parenthesis slowly
> ------------------------------------------------------------
>
>                 Key: JEXL-97
>                 URL: https://issues.apache.org/jira/browse/JEXL-97
>             Project: Commons JEXL
>          Issue Type: Bug
>    Affects Versions: 1.1
>         Environment: Java
>            Reporter: Jeff Ichnowski
>            Priority: Minor
>             Fix For: 2.0
>
>         Attachments: proposed.patch
>
>
> JEXL's parser uses an unbounded JavaCC LOOKAHEAD to distinguish assignment expressions
from other expressions.  The result is certain expressions take exponential time to parse.
 The example snippet below demonstrates the problem.  On my machine parsing the expression
below takes ~120 seconds.  Changing the parser to remove the LOOKAHEAD can get this to parse
in milliseconds.  The lookahead appears to be in all versions of the parser source.
> import org.apache.commons.jexl.Expression;
> import org.apache.commons.jexl.ExpressionFactory;
> public class SlowParse {
>     public static void main(String[] args) throws Exception {
>         String input = 
>             "(((((((((((((((((((((((((z+y)/x)*w)-v)*u)/t)-s)*r)/q)+p)-o)*n)-m)+l)*k)+j)/i)+h)*g)+f)/e)+d)-c)/b)+a)";
>         // Make sure everything is loaded...
>         Expression expr = ExpressionFactory.createExpression(input);
>         long start = System.nanoTime();
>         expr = ExpressionFactory.createExpression(input);
>         long end = System.nanoTime();
>         System.out.printf("Parse took %.1f seconds\n", (end-start)/1e+9);
>     }
> }

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