Re: Exception handling

From:
Lew <lew@lewscanon.com>
Newsgroups:
comp.lang.java.programmer
Date:
Mon, 30 Nov 2009 10:49:14 -0800 (PST)
Message-ID:
<ab85fdb4-c347-4917-81e8-4d9a172b5078@m11g2000vbo.googlegroups.com>
Lew wrote:

It could be said that chained exceptions are a better choice.

  /** Throwable chainer.
   * @param trow Throwable to chain.
   * @param log Logger with which to log the chain.
   */
  public static void chain( Throwable trow, Logger log )
  {
    for ( Throwable last = null, thr = trow;
          thr != null && thr != last;
          thr = (last = thr).getCause() )
    {
      log.debug( thr.getLocalizedMessage() );
    }
  }


Pitch wrote:

I don't get this. If you are just trying to log all causes, why not use
logger?


Lew wrote:

A) this does use a logger,


Pitch wrote:

Well, if you use Logger implemetation form Apache.org, this does exactly
what you code does (but in fewer lines):

log.error(this, null, trow);


Exactly what I coded? It uses getLocalizedMessage() and does not
display a stack trace? For all logging libraries? Are you quite
sure?

Lew:

B) the purpose isn't to show logging but chaining.


Pitch wrote:

So you say inheritance is not the way to go? We should look through the
chained-exceptions to find out if we need to handle a general exception
or not? Doesn't that clutter the code with loops and if-statements?


I said it was an alternative, and quite a useful one when the
exceptions are not hierarchically related. In general one cannot
ensure that all exceptions are hierarchically related, and when one
wraps and rethrows with a lower-level exception as a cause, chaining
is the only way to go.

Lew:

If you think I was "just trying to log all causes" then you missed the p=

oint.

Pitch wrote:

Well, why don't you explain if you think I misunderstood something? Or
is it that you think your time is too valuable for a simple explanation?


It was explained in my post to which you originally replied.
I said:

It could be said that chained exceptions are a better choice.


Clearly from that you can see that my point was about chained
exceptions, no?

Stow your sarcasm; it was you who missed the point, not I who failed
to explain it.

Pitch wrote:

Anyway I think you're completely wrong and I wouldn't suggest to anyone
to use this approach.


Too bad for the people you're advising, then. Exception chaining is a
very powerful tool and quite usually the only way to get at root
causes, and it's quite standard throughout the Java universe/

--
Lew

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