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Re: Logging Question

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On Wed, 4 Jan 2012, Arved Sandstrom wrote:

> On 12-01-03 11:33 AM, Tom Anderson wrote:
>> On Sun, 1 Jan 2012, Arved Sandstrom wrote:
>>
>>> It would better to regard each record as a separate well-formed XML 
>>> document, and the file is merely physical storage for a bunch of log 
>>> records.
>>
>> What happens if you throw such a file into a normal XML parser? 
>> well-formedness checking they do.
>
> One thing that works with stream parsing is to fool the parser with a 
> fake starting document element tag...like <log>. :-) Given that, SAX or 
> StAX will parse forever, or until end of file/stream anyway.
>
> If you didn't fake out the parser it would choke with a well-formedness 
> error after the first "record".

Okay.

> You can get quite innovative (read hackish) by doing stuff like:
>
> final ByteArrayInputStream bsBegin =
>  new ByteArrayInputStream("<wrapper>".getBytes());
> URL fileUrl = new URL(...);
> final InputStream in = fileUrl.openStream();
> final ByteArrayInputStream bsEnd =
>  new ByteArrayInputStream("</wrapper>".getBytes());
>
> SequenceInputStream sis = new SequenceInputStream(

Always good to see SequenceInputStream!

> new Enumeration() {
>
>  int index = 0;
>  InputStream streams[] = new InputStream[] {bsBegin, in, bsEnd};
>
>  @Override
>  public boolean hasMoreElements() {
>    return index < streams.length;
>  }
>
>  @Override
>  public Object nextElement() {
>    return streams[index++];
>  }
>
> });

Perhaps easier to do Collections.enumeration(Arrays.asList(bsBegin, in, bsEnd)).

> The point here being is that the "real" input wasn't well-formed at all, 
> but by the time the parser sees it, it's fine.

Yes, good trick. As a general pattern (topping and tailing some stream of 
items with start-container and end-container markers), it's useful in all 
sorts of places. Admittedly most when dealing with XML.

> Completely different approach, and it might even be the most "valid" 
> approach, would be to consider each log "record" to be an XML fragment.

Is there any support for getting parsers to parse multiple fragments from 
a single stream? If not, we're back to needing to frame the stream in some 
way, and then we might as well parse it as a sequence of documents. I'm 
pretty hazy on what the point of document fragments is, really.

tom

-- 
music is a interesting thing, DUN COMPARE AND PUT IT TO BLAR BLAR GENRE,
THIS IS A STUPID ACT......MUSIC IS SAME TO EVERYONE -- sihamze

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Logging Question Novice <novice@example..com> - 2011-12-31 21:27 +0000
  Re: Logging Question Jeff Higgins <jeff@invalid.invalid> - 2011-12-31 17:25 -0500
    Re: Logging Question Novice <novice@example..com> - 2012-01-01 01:46 +0000
  Re: Logging Question Lew <lewbloch@gmail.com> - 2011-12-31 14:53 -0800
    Re: Logging Question Novice <novice@example..com> - 2012-01-01 01:59 +0000
      Re: Logging Question Jeff Higgins <jeff@invalid.invalid> - 2011-12-31 22:14 -0500
        Re: Logging Question Novice <novice@example..com> - 2012-01-01 05:44 +0000
          Re: Logging Question Jeff Higgins <jeff@invalid.invalid> - 2012-01-01 07:59 -0500
            Re: Logging Question Jeff Higgins <jeff@invalid.invalid> - 2012-01-01 08:14 -0500
            Re: Logging Question Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-01-01 19:06 -0400
              Re: Logging Question Jeff Higgins <jeff@invalid.invalid> - 2012-01-01 18:24 -0500
              Re: Logging Question Tom Anderson <twic@urchin.earth.li> - 2012-01-03 15:33 +0000
                Re: Logging Question Jeff Higgins <jeff@invalid.invalid> - 2012-01-03 11:21 -0500
                Re: Logging Question Jeff Higgins <jeff@invalid.invalid> - 2012-01-03 11:35 -0500
                Re: Logging Question Tom Anderson <twic@urchin.earth.li> - 2012-01-04 14:42 +0000
                Re: Logging Question Jeff Higgins <jeff@invalid.invalid> - 2012-01-04 11:43 -0500
                Re: Logging Question Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-01-04 20:28 -0400
                Re: Logging Question Donkey Hottie <donkey@fredriksson.dy.fi> - 2012-01-05 11:28 +0200
                Re: Logging Question Tom Anderson <twic@urchin.earth.li> - 2012-01-08 14:08 +0000
                Re: Logging Question Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-01-09 19:47 -0400

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