Details

    • Type: Improvement Improvement
    • Status: Closed
    • Priority: Minor Minor
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 1.5
    • Component/s: Engine
    • Labels:
      None

      Description

      Thought it might be useful to archive the brief discussion on this topic since it's a cross-cutting type of issue. I'm going to link to this issue in the change log.

      ----- Original Message -----
      From: "Will Glass-Husain" <wglass@forio.com>
      To: <velocity-dev@jakarta.apache.org>
      Sent: Monday, January 02, 2006 7:03 AM
      Subject: RuntimeExceptions

      First, happy new year to the Velocity developer community...

      I've been pondering how Velocity handles exceptions. Right now, almost every call to a plugin has a catch-all Exception handler which does little more than log the Exception. There's been a couple of requests in the past few months to pass RuntimeExceptions or similar through.

      • In Velocity-424, Malcolm Edgar wanted NPEs from a call to toString to pass through a #parse. (we did this).
      • Llewelyn Falco created a "TestableUberspect" which interrupted processing upon an invalid method call.
      • There was someone else (can't find the reference) who wanted to interrupt processing when confronted with an invalid method call.

      I was wondering, why does Velocity intercept every exception? Isn't the point of a RuntimeException that it signals an application-level problem that should be returned to the calling code? In addition, we should allow plugins (event handlers, uberspectors, resource loaders) to interrupt processing for critical problems. To me, there seems three choices.

      (1) Catch every unexpected condition and do something with it (e.g. catch NPE from toString() and wrap it in a MethodInvocationException). Logging does not count as doing something.

      (2) Create a special VelocityRuntimeException that plugins can use to interrupt processing. Every generic catch (Exception E) wrapper would pass this through. (I've coded this though not applied the patch).

      (3) Remove all generic Exception catch's. (or if not feasible, always pass RuntimeException's through).

      To me, option #1 seems infeasible. (if we start wrapping toString, we'd need to wrap a lot of other little stuff). Option #2 is useful for plugins to interrupt processing. But I'm wondering, why not do option #3 and just pass through all RuntimeExceptions. Any reason why we should be catching unexpected RuntimeException's?

      Appreciate other thoughts...

      Best,
      WILL

        Activity

        Hide
        Will Glass-Husain added a comment -

        Brief summary of comments...

        Malcom Edgar:
        +1 on Option #3. I think this is now accepted as a best practice with Java error handling.

        Peter Urban:
        Yes, please... it would make life with Velocity a lot easier!

        Llewellyn Falco:
        +1
        I especially agree with the removal of any exception handling where the
        handling is to log the error. as my log files are not read nearly often
        enough for this to work.

        Nathan Bubna:
        hmm. i'm a bit skeptical of whether all the generic Exception catches
        can be removed, but i'm pretty sure i'd be supportive of passing all
        (or at least most) RuntimeExceptions through. i personally haven't
        hit any problems with the current pattern, but i'm sure things could
        be improved. +0.5 for option 3.

        Show
        Will Glass-Husain added a comment - Brief summary of comments... Malcom Edgar: +1 on Option #3. I think this is now accepted as a best practice with Java error handling. Peter Urban: Yes, please... it would make life with Velocity a lot easier! Llewellyn Falco: +1 I especially agree with the removal of any exception handling where the handling is to log the error. as my log files are not read nearly often enough for this to work. Nathan Bubna: hmm. i'm a bit skeptical of whether all the generic Exception catches can be removed, but i'm pretty sure i'd be supportive of passing all (or at least most) RuntimeExceptions through. i personally haven't hit any problems with the current pattern, but i'm sure things could be improved. +0.5 for option 3.
        Hide
        Will Glass-Husain added a comment -

        Update applied.

        Show
        Will Glass-Husain added a comment - Update applied.
        Hide
        Henning Schmiedehausen added a comment -

        Close all resolved issues for Engine 1.5 release.

        Show
        Henning Schmiedehausen added a comment - Close all resolved issues for Engine 1.5 release.

          People

          • Assignee:
            Will Glass-Husain
            Reporter:
            Will Glass-Husain
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              Updated:
              Resolved:

              Development