You are missing the point. The ‘parser’
is not the SAXParser class. The parser itself (the
scanner is what it is called) is inside of the various DOMParser,
SAXParser, etc… Those are just wrappers around
the scanner. You can, as a worst case fallback, always just override say the DOMParser class, which itself implements the scanner’s
callback’s and plugs itself into the scanner. It then gets error
callbacks (and other kinds of callbacks) from the scanner, which it then turns
around and passes out through whatever APIs available for a particular type of
interface, e.g. SAX, SAX2, DOM.
The internal callbacks from the scanner
provide all of the information that is possibly available. The fact that some
of that information gets dropped on the way out via a particular API doesn’t
mean that the data isn’t available, it just means that perhaps the API
you are using to get the data out doesn’t provide a means to get all of
the data out.
But, if you derive from the DOMParser class, for instance, and override the virtual
method that it uses to get error callbacks, you can get the internal callbacks from
the scanner, which has all of the available info in it. You can look at that
info, and then pass it on the parent class for regular processing.
I’m not saying you really need to do
that in this case, since it might just be that you don’t understand the
SAX2 API well enough to know how it gives you errors. But, when there is no
other way to get certain info, you can always do it this way.
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]
Sent: Tuesday, September 24, 2002 6:43 PM
To: [EMAIL PROTECTED]
Cc: [EMAIL PROTECTED]
Subject: RE: How to get the error
code during SAX parse?
The error handler is not given the actual error code,
only one of
XMLErrs::XMLException_Fatal
XMLErrs::XMLException_Error
XMLErrs::XMLException_Warning
and
hence my issue ...
Is
there good reason to 'mask' the actual error that occured? If not maybe
it can be resolved by a simple change to XMLScanner::scanDocument so that the
actual error code is passed through to the error handler.
|
|
Dean Roddey
<[EMAIL PROTECTED]>
25/09/2002 11:35 AM
Please
respond to xerces-c-dev
|
To: [EMAIL PROTECTED]
cc:
Subject: RE: How to get the
error code during SAX parse?
|
Oh ok, I forgot that there was a change a while
back to get the 'file not found' stuff into the block that reports via the
error handler. But the error handler does report the error codes. If the SAX2
specification doesn't provide for that error code to be passed on to the client
app, then I guess that's just the way it is. Its not a problem with Xerces, but
just with the error callback interface of SAX2. As I said, I've not looked at
that interface, so I can't say.
If that is the case, you
can still do it. Just provide your own derivative of the SAX2 parser, and
override the error callback on the parser object, looking at the raw error
callback info, then passing it back to the underlying SAX2 parser for normal
processing. I don't know if that's really necessary, since I've not looked at
the SAX2 interfaces, and perhaps you just missing something. But that's always
a way to get to the raw parser callbacks.
-------------------------------------
Dean Roddey
The Charmed Quark
Controller
[EMAIL PROTECTED]
www.charmedquark.com
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]
Sent: Tuesday, September 24, 2002 5:44 PM
To: [EMAIL PROTECTED]
Subject: RE: How to get the error code during SAX parse?
I am not sure what you mean. XMLScanner traps the exception when the
target file does not exist (for example). This means that the
caller (eg DOMCount) does not get told the file does not exist - only that
'there was an error' via the call back.
There is no difference in the behaviour the caller sees if there error was due
to file not existing or document being malformed in terms of whether or not an
exception is thrown or the callback is called.
In other words:
- 'fundamental errors with finding the source data' are reported via the call
back 'as parsing errors' if I understand what you are saying.
- in DOMCount the catches around the call to parse documents will only catch
something if the code was changed to try parsing another document whilst a
parse is in progress or similar.
In the case that the target files does not exist the caller has no way of
knowing what the actual error was without parsing the error message (which is a
bit ugly) ...
Are you implying that the exception handling in XMLScanner::scanDocument should
actually be removed/altered to allow these 'fundamental' errors to be thrown
back to the caller?
|
|
Dean Roddey
<[EMAIL PROTECTED]>
25/09/2002 10:13 AM
Please respond to xerces-c-dev
|
To: [EMAIL PROTECTED]
cc:
Subject: RE: How to get
the error code during SAX parse?
|
As I said, exceptions are not used to report parsing errors, only fundamental
errors with finding the source data, so the catch after the parse is irrelevant
for parsing errors. Look at the error handler code for the DOMPrint and
DOMCount examples.
-------------------------------------
Dean Roddey
The Charmed Quark
Controller
[EMAIL PROTECTED]
www.charmedquark.com
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]
Sent: Tuesday, September 24, 2002 4:30 PM
To: [EMAIL PROTECTED]
Cc: [EMAIL PROTECTED]
Subject: RE: How to get the error code during SAX parse?
But I'm saying none of the parsers don't supply the information I'd like (ie
the actual parsing error that occurred) because the underlying scanner which is
used by both DOM and SAX parsers throws the error away ...
See XMLScanner::scanDocument - the exception handling that is invoked (if file
does not exist for example).
|
|
Dean Roddey
<[EMAIL PROTECTED]>
25/09/2002 09:23 AM
Please respond to xerces-c-dev
|
To: [EMAIL PROTECTED]
cc:
Subject: RE: How to get the
error code during SAX parse?
|
I can't speak to the SAX2 part, since I've not looked at that variant. The
parser itself does provide the information you want, but if the SAX2
specification (which the Xerces team does not define) doesn't provide a way to
pass it on, then there's not much the parser can do about it.
-------------------------------------
Dean Roddey
The Charmed Quark
Controller
[EMAIL PROTECTED]
www.charmedquark.com
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]
Sent: Tuesday, September 24, 2002 4:13 PM
To: [EMAIL PROTECTED]
Subject: RE: How to get the error code during SAX parse?
Can we get some enlightenment on this (for the dummies!).
When you say the pluggable error call backs, do you mean the things you set by
calling SAX2XMLReader::setErrorHandler or SAXParser::setErrorHandler?
If so, then these are passed a SAXParseException object which does not have an
error code.
If not, which example should we look at?
>From previous discussions, even if the SAXParseException object contained
an error code it would only be one of
XMLErrs::XMLException_Fatal
XMLErrs::XMLException_Error
XMLErrs::XMLException_Warning
because XMLScanner::scanDocument basically chucks away the actual error.
So, to get the actual error code that occurred during a parse you have to hack
the Xerces code base ...
Would it make sense if the scanner passed through the actual error code to
XMLScanner::emitError and thence to its error reporter? Then each of the
error reporters for each parser can take the appropriate action (and one could
then simply subclass the relevant parser and overload the error function to
trap the actual error code).
To me there is a bit of an issue in that it is not easy to take programatic
action according to the parser failure (eg take action depending if document
was well formed but not valid versus malformed versus file does not exist).
What do people think?
Am I missing something?
|
|
Dean Roddey
<[EMAIL PROTECTED]>
25/09/2002 08:27 AM
Please respond to xerces-c-dev
|
To: [EMAIL PROTECTED]
cc:
Subject: RE: How to get the
error code during SAX parse?
|
Errors are not reported via the exceptions, they are reported via pluggable
error callbacks. An exception can only report one error, because it unwinds the
stack. The callbacks allow the parser to continue through more than one error
(if you tell it that's ok to do.) Look at the sample programs, which clearly
show how this is done.
-------------------------------------
Dean Roddey
The Charmed Quark
Controller
[EMAIL PROTECTED]
www.charmedquark.com
-----Original Message-----
From: Scot Nielsen [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, September 24, 2002 3:09 PM
To: 'Xerces-Dev (E-mail)'
Subject: How to get the error code during SAX parse?
Can someone
enlighten me please? There's no error code value in the SaxParseException
class...
Are all error codes
for internal use only?
Many thanks, Scot
Nielsen
