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J
JocularGargoyle
Participating Frequently
June 3, 2009
Question

Only on first request: "null pointers are another name for undefined values"

  • June 3, 2009
  • 2 replies
  • 1582 views

We recently updated from CF7 to CF8 and have started getting the following error:

===========
The system has attempted to use an undefined value, which usually indicates a programming error, either in your code or some system code.

Null Pointers are another name for undefined values.
===========

However, it doesn't occur every time you load the page. In fact, it only occurs the first time you load the page. If you hit refresh, it's fine. If you hit refresh again, it's still fine. Visit it a little bit later, still fine. Visit it a day later? The error might be back.

We're using MySQL and not doing anything weird with the queries. For example:

<cfquery name="qGetJobs" datasource="#APPLICATION.dsn#">
SELECT * FROM jobs ORDER BY dateposted DESC

</cfquery>

(Incidentally, dateposted is a timestamp and not empty in any record.)

I've searched the forums here and found several people receiving the same error, but they're not magically fixing themselves on refresh. I did find a post on an other site that solved the problem by recreating the CF DSN.

Do you have any idea why this might be happening? Thanks!


    This topic has been closed for replies.

    2 replies

    J
    JocularGargoyleAuthor
    Participating Frequently
    June 4, 2009

    Apparently the fix for this particular issue is to uncheck 'Maintain connections across client requests' in the Advanced settings for the ColdFusion DSN. This hardly seems ideal since every request will have to open a connection, do the query, and close, but I suppose that's preferable to the occasional error. Thank you, everyone, for your help!

    T
    TLC-IT
    Inspiring
    June 5, 2009

    It might be... but what if instead you catch the error (if it occurs) and do something to deal with the error on the rare occasion when it happens?

    From your description, it seems that the problem is "the connection has been lost."  Okay, that's a very-occasional thing (so you say...), doesn't happen too often, and so the real issue (one might say...) is that the end-user sees it happening with a very-ugly error message.

    If you frame the logic in a try..catch block, the exception will be trapped when it occurs and then you can take whatever recovery-action you might need to do (e.g. re-establish the connection and try again...).  Most of the time, the exception doesn't happen and you just go on your merry way, having not wasted any time laboriously checking to see whether the error happened or not.  You just stick someone out there in right-field to catch the ball if, this time, it happens to "go foul."  It costs next-to-nothing to post him out there, and he only has something to do when-and-if "the rare circumstance that he is looking for" actually happens.  (You don't have to say ... "if the ball went foul then..."  If the ball went foul, as it does 2%-or-less of the time, then your right-fielder unerringly catches it and that's how you know.)

    Offhand, I think that this would be a lot less costly than maintaining a bunch of connections.  (I opine that such an approach would prove to be a decision that you regret for other reasons.)

    The term, "exception," is well-named.  Take advantage of them.

    ilssac
    ilssac
    Inspiring
    June 3, 2009

    My first guess based on the tiny bit of code you shown, is that "Application.dsn" is not defiend when the query is first run, but afterwords it gets defined and then works until such a time is it expires.


    But there could be other causes of this error that exist somewhere else in the application.

    J
    JocularGargoyleAuthor
    Participating Frequently
    June 3, 2009

    We'd actually considered that, but even if I replace APPLICATION.dsn with the actual datasource name the problem persists. Thanks for offering that up though!

    ilssac
    ilssac
    Inspiring
    June 3, 2009

    Well what part of the code is the error actually pointing to and what does the code at that point do?

    98.73% of time NULL pointer is just an awkward way to say 'undefined variable'.

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