XML::Checker::Parser
XML::Checker::Parser(3User Contributed Perl DocumentatiXML::Checker::Parser(3)
NAME
XML::Checker::Parser - an XML::Parser that validates at parse time
SYNOPSIS
use XML::Checker::Parser;
my %expat_options = (KeepCDATA => 1,
Handlers => [ Unparsed => \&my_Unparsed_handler ]);
my $parser = new XML::Checker::Parser (%expat_options);
eval {
local $XML::Checker::FAIL = \&my_fail;
$parser->parsefile ("fail.xml");
};
if ($@) {
# Either XML::Parser (expat) threw an exception or my_fail() died.
... your error handling code here ...
}
# Throws an exception (with die) when an error is encountered, this
# will stop the parsing process.
# Don't die if a warning or info message is encountered, just print a message.
sub my_fail {
my $code = shift;
die XML::Checker::error_string ($code, @_) if $code < 200;
XML::Checker::print_error ($code, @_);
}
DESCRIPTION
XML::Checker::Parser extends XML::Parser
I hope the example in the SYNOPSIS says it all, just use
XML::Checker::Parser as if it were an XML::Parser. See XML::Parser for
the supported (expat) options.
You can also derive your parser from XML::Checker::Parser instead of
from XML::Parser. All you should have to do is replace:
package MyParser;
@ISA = qw( XML::Parser );
with:
package MyParser;
@ISA = qw( XML::Checker::Parser );
XML::Checker::Parser constructor
$parser = new XML::Checker::Parser (SkipExternalDTD => 1, SkipInsignifWS => 1);
The constructor takes the same parameters as XML::Parser with the fol-
lowing additions:
SkipExternalDTD
By default, it will try to load external DTDs using LWP. You can
disable this by setting SkipExternalDTD to 1. See External DTDs for
details.
SkipInsignifWS
By default, it will treat insignificant whitespace as regular Char
data. By setting SkipInsignifWS to 1, the user Char handler will
not be called if insignificant whitespace is encountered. See
"INSIGNIFICANT_WHITESPACE" in XML::Checker for details.
LWP_UserAgent
When calling parsefile() with a URL (instead of a filename) or when
loading external DTDs, we use LWP to download the remote file. By
default it will use a LWP::UserAgent that is created as follows:
use LWP::UserAgent;
$LWP_USER_AGENT = LWP::UserAgent->new;
$LWP_USER_AGENT->env_proxy;
Note that env_proxy reads proxy settings from your environment
variables, which is what I need to do to get thru our firewall. If
you want to use a different LWP::UserAgent, you can either set it
globally with:
XML::Checker::Parser::set_LWP_UserAgent ($my_agent);
or, you can specify it for a specific XML::Checker::Parser by pass-
ing it to the constructor:
my $parser = new XML::Checker::Parser (LWP_UserAgent => $my_agent);
Currently, LWP is used when the filename (passed to parsefile)
starts with one of the following URL schemes: http, https, ftp,
wais, gopher, or file (followed by a colon.) If I missed one,
please let me know.
The LWP modules are part of libwww-perl which is available at CPAN.
External DTDs
XML::Checker::Parser will try to load and parse external DTDs that are
referenced in DOCTYPE definitions unless you set the SkipExternalDTD
option to 1 (the default setting is 0.) See CAVEATS for details on
what is not supported by XML::Checker::Parser.
XML::Parser (version 2.27 and up) does a much better job at reading
external DTDs, because recently external DTD parsing was added to
expat. Make sure you set the XML::Parser option ParseParamEnt to 1 and
the XML::Checker::Parser option SkipExternalDTD to 1. (They can both
be set in the XML::Checker::Parser constructor.)
When external DTDs are parsed by XML::Checker::Parser, they are located
in the following order:
o With the %URI_MAP, which can be set using map_uri. This hash maps
external resource ids (like system ID's and public ID's) to full
path URI's. It was meant to aid in resolving PUBLIC IDs found in
DOCTYPE declarations after the PUBLIC keyword, e.g.
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN">
However, you can also use this to force XML::Checker to read DTDs
from a different URL than was specified (e.g. from the local file
system for performance reasons.)
o on the Internet, if their system identifier starts with a protocol
(like http://...)
o on the local disk, if their system identifier starts with a slash
(absolute path)
o in the SGML_SEARCH_PATH, if their system identifier is a relative
file name. It will use @SGML_SEARCH_PATH if it was set with
set_sgml_search_path(), or the colon-separated
$ENV{SGML_SEARCH_PATH}, or (if that isn't set) the list (".",
"$ENV{'HOME'}/.sgml", "/usr/lib/sgml", "/usr/share/sgml"), which
includes the current directory, so it should do the right thing in
most cases.
Static methods related to External DTDs
set_sgml_search_path (dir1, dir2, ...)
External DTDs with relative file paths are looked up using the
@SGML_SEARCH_PATH, which can be set with this method. If
@SGML_SEARCH_PATH is never set, it will use the colon-separated
$ENV{SGML_SEARCH_PATH} instead. If neither are set it uses the
list: ".", "$ENV{'HOME'}/.sgml", "/usr/lib/sgml",
"/usr/share/sgml".
set_sgml_search_path is a static method.
map_uri (pubid => uri, ...)
To define the location of PUBLIC ids, as found in DOCTYPE declara-
tions after the PUBLIC keyword, e.g.
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN">
call this method, e.g.
XML::Checker::Parser::map_uri (
"-//W3C//DTD HTML 4.0//EN" => "file:/user/html.dtd");
See External DTDs for more info.
XML::Checker::Parser::map_uri is a static method.
Switching user handlers at parse time
You should be able to use setHandlers() just as in XML::Parser. (Using
setHandlers has not been tested yet.)
Error handling
XML::Checker::Parser routes the fail handler through
XML::Checker::Parser::fail_add_context() before calling your fail han-
dler (i.e. the global fail handler: $XML::Checker::FAIL. See
"ERROR_HANDLING" in XML::Checker.) It adds the (line, column, byte)
information from XML::Parser to the error context (unless it was the
end of the XML document.)
Supported XML::Parser handlers
Only the following XML::Parser handlers are currently routed through
XML::Checker: Init, Final, Char, Start, End, Element, Attlist, Doctype,
Unparsed, Notation.
CAVEATS
When using XML::Checker::Parser to parse external DTDs (i.e. with
SkipExternalDTD => 0), expect trouble when your external DTD contains
parameter entities inside declarations or conditional sections. The
external DTD should probably have the same encoding as the orignal XML
document.
AUTHOR
Send bug reports, hints, tips, suggestions to Enno Derksen at
<enno@att.com>.
SEE ALSO
XML::Checker ("SEE_ALSO" in XML::Checker), XML::Parser
perl v5.8.0 2000-01-31 XML::Checker::Parser(3)
