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LibXSLT(3) |
User Contributed Perl Documentation |
LibXSLT(3) |
XML::LibXSLT - Interface to the GNOME libxslt library
use XML::LibXSLT;
use XML::LibXML;
my $xslt = XML::LibXSLT->new();
my $source = XML::LibXML->load_xml(location => 'foo.xml');
my $style_doc = XML::LibXML->load_xml(location=>'bar.xsl', no_cdata=>1);
my $stylesheet = $xslt->parse_stylesheet($style_doc);
my $results = $stylesheet->transform($source);
print $stylesheet->output_as_bytes($results);
This module is an interface to the GNOME project's libxslt. This is an extremely
good XSLT engine, highly compliant and also very fast. I have tests showing
this to be more than twice as fast as Sablotron.
XML::LibXSLT has some global options. Note that these are probably not thread or
even fork safe - so only set them once per process. Each one of these options
can be called either as class methods, or as instance methods. However either
way you call them, it still sets global options.
Each of the option methods returns its previous value, and can be
called without a parameter to retrieve the current value.
- max_depth
-
XML::LibXSLT->max_depth(1000);
This option sets the maximum recursion depth for a stylesheet.
See the very end of section 5.4 of the XSLT specification for more
details on recursion and detecting it. If your stylesheet or XML file
requires seriously deep recursion, this is the way to set it. Default
value is 250.
- max_vars
-
XML::LibXSLT->max_vars(100_000);
This option sets the maximum number of variables for a
stylesheet. If your stylesheet or XML file requires many variables, this
is the way to increase their limit. Default value is system-specific and
may vary.
- debug_callback
-
XML::LibXSLT->debug_callback($subref);
Sets a callback to be used for debug messages. If you don't
set this, debug messages will be ignored.
- register_function
-
XML::LibXSLT->register_function($uri, $name, $subref);
$stylesheet->register_function($uri, $name, $subref);
Registers an XSLT extension function mapped to the given URI.
For example:
XML::LibXSLT->register_function("urn:foo", "bar",
sub { scalar localtime });
Will register a "bar"
function in the "urn:foo" namespace
(which you have to define in your XSLT using
"xmlns:...") that will return the
current date and time as a string:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:foo="urn:foo">
<xsl:template match="/">
The time is: <xsl:value-of select="foo:bar()"/>
</xsl:template>
</xsl:stylesheet>
Parameters can be in whatever format you like. If you pass in
a nodelist it will be a XML::LibXML::NodeList object in your perl code,
but ordinary values (strings, numbers and booleans) will be ordinary
perl scalars. If you wish them to be
"XML::LibXML::Literal",
"XML::LibXML::Number" and
"XML::LibXML::Number" values
respectively then set the variable
$XML::LibXSLT::USE_LIBXML_DATA_TYPES to a true
value. Return values can be a nodelist or a plain value - the code will
just do the right thing. But only a single return value is supported (a
list is not converted to a nodelist).
- register_element
-
$stylesheet->register_element($uri, $name, $subref)
Registers an XSLT extension element
$name mapped to the given URI. For example:
$stylesheet->register_element("urn:foo", "hello", sub {
my $name = $_[2]->getAttribute( "name" );
return XML::LibXML::Text->new( "Hello, $name!" );
});
Will register a "hello"
element in the "urn:foo" namespace
that returns a "Hello, X!" text node. You must define this
namespace in your XSLT and include its prefix in the
"extension-element-prefixes" list:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:foo="urn:foo"
extension-element-prefixes="foo">
<xsl:template match="/">
<foo:hello name="bob"/>
</xsl:template>
</xsl:stylesheet>
The callback is passed the input document node as
$_[1] and the stylesheet node as
$_[2]. $_[0] is reserved
for future use.
The following methods are available on the new XML::LibXSLT object:
- parse_stylesheet($stylesheet_doc)
- $stylesheet_doc here is an XML::LibXML::Document
object (see XML::LibXML) representing an XSLT file. This method will
return a XML::LibXSLT::Stylesheet object, or undef on failure. If the XSLT
is invalid, an exception will be thrown, so wrap the call to
parse_stylesheet in an eval{} block to trap this.
IMPORTANT: $stylesheet_doc should not
contain CDATA sections, otherwise libxslt may misbehave. The best way to
assure this is to load the stylesheet with no_cdata flag, e.g.
my $stylesheet_doc = XML::LibXML->load_xml(location=>"some.xsl", no_cdata=>1);
- parse_stylesheet_file($filename)
- Exactly the same as the above, but parses the given filename
directly.
To define XML::LibXSLT or XML::LibXSLT::Stylesheet specific input callbacks,
reuse the XML::LibXML input callback API as described in
XML::LibXML::InputCallback(3).
- input_callbacks($icb)
- Enable the callbacks in $icb only for this
XML::LibXSLT object. $icb should be a
"XML::LibXML::InputCallback" object.
This will call "init_callbacks" and
"cleanup_callbacks" automatically during
parsing or transformation.
To create security preferences for the transformation see
XML::LibXSLT::Security. Once the security preferences have been defined you
can apply them to an XML::LibXSLT or XML::LibXSLT::Stylesheet instance using
the "security_callbacks()" method.
The main API is on the stylesheet, though it is fairly minimal.
One of the main advantages of XML::LibXSLT is that you have a
generic stylesheet object which you call the transform() method
passing in a document to transform. This allows you to have multiple
transformations happen with one stylesheet without requiring a reparse.
- transform(doc, %params)
-
my $results = $stylesheet->transform($doc, foo => "'bar'");
print $stylesheet->output_as_bytes($results);
Transforms the passed in XML::LibXML::Document object, and
returns a new XML::LibXML::Document. Extra hash entries are used as
parameters. Be sure to keep in mind the caveat with regard to quotes
explained in the section on "Parameters" below.
- transform_file(filename, %params)
-
my $results = $stylesheet->transform_file($filename, bar => "'baz'");
Note the string parameter caveat, detailed in the section on
"Parameters" below.
- output_as_bytes(result)
- Returns a scalar that is the XSLT rendering of the XML::LibXML::Document
object using the desired output format (specified in the xsl:output tag in
the stylesheet). Note that you can also call
$result->toString, but that will *always*
output the document in XML format which may not be what you asked for in
the xsl:output tag. The scalar is a byte string encoded in the output
encoding specified in the stylesheet.
- output_as_chars(result)
- Like "output_as_bytes(result)", but
always return the output as (UTF-8 encoded) string of characters.
- output_string(result)
- DEPRECATED: This method is something between
"output_as_bytes(result)" and
"output_as_bytes(result)": The scalar
returned by this function appears to Perl as characters (UTF8 flag is on)
if the output encoding specified in the XSLT stylesheet was UTF-8 and as
bytes if no output encoding was specified or if the output encoding was
other than UTF-8. Since the behavior of this function depends on the
particular stylesheet, it is deprecated in favor of
"output_as_bytes(result)" and
"output_as_chars(result)".
- output_fh(result, fh)
- Outputs the result to the filehandle given in
$fh.
- output_file(result, filename)
- Outputs the result to the file named in
$filename.
- output_encoding()
- Returns the output encoding of the results. Defaults to
"UTF-8".
- output_method()
- Returns the value of the "method"
attribute from "xsl:output" (usually
"xml",
"html" or
"text"). If this attribute is
unspecified, the default value is initially
"xml". If the transform method is used
to produce an HTML document, as per the XSLT spec
<http://www.w3.org/TR/xslt#output>, the default value will change to
"html". To override this behavior
completely, supply an "xsl:output"
element in the stylesheet source document.
- media_type()
- Returns the value of the "media-type"
attribute from "xsl:output". If this
attribute is unspecified, the default media type is initially
"text/xml". This default changes to
"text/html" under the same conditions as
output_method.
- input_callbacks($icb)
- Enable the callbacks in $icb only for this
stylesheet. $icb should be a
"XML::LibXML::InputCallback" object.
This will call "init_callbacks" and
"cleanup_callbacks" automatically during
transformation.
LibXSLT expects parameters in XPath format. That is, if you wish to pass a
string to the XSLT engine, you actually have to pass it as a quoted string:
$stylesheet->transform($doc, param => "'string'");
Note the quotes within quotes there!
Obviously this isn't much fun, so you can make it easy on
yourself:
$stylesheet->transform($doc, XML::LibXSLT::xpath_to_string(
param => "string"
));
The utility function does the right thing with respect to strings
in XPath, including when you have quotes already embedded within your
string.
Provides an interface to the libxslt security framework by allowing callbacks to
be defined that can restrict access to various resources (files or URLs)
during a transformation.
The libxslt security framework allows callbacks to be defined for
certain actions that a stylesheet may attempt during a transformation. It
may be desirable to restrict some of these actions (for example, writing a
new file using exsl:document). The actions that may be restricted are:
- read_file
- Called when the stylesheet attempts to open a local file (ie: when using
the document() function).
- write_file
- Called when an attempt is made to write a local file (ie: when using the
exsl:document element).
- create_dir
- Called when a directory needs to be created in order to write a file.
NOTE: By default, create_dir is not allowed. To enable it a
callback must be registered.
- read_net
- Called when the stylesheet attempts to read from the network.
- write_net
- Called when the stylesheet attempts to write to the network.
The interface for this module is similar to XML::LibXML::InputCallback. After
creating a new instance you may register callbacks for each of the security
options listed above. Then you apply the security preferences to the
XML::LibXSLT or XML::LibXSLT::Stylesheet object using
"security_callbacks()".
my $security = XML::LibXSLT::Security->new();
$security->register_callback( read_file => $read_cb );
$security->register_callback( write_file => $write_cb );
$security->register_callback( create_dir => $create_cb );
$security->register_callback( read_net => $read_net_cb );
$security->register_callback( write_net => $write_net_cb );
$xslt->security_callbacks( $security );
-OR-
$stylesheet->security_callbacks( $security );
The registered callback functions are called when access to a
resource is requested. If the access should be allowed the callback should
return 1, if not it should return 0. The callback functions should accept
the following arguments:
- $tctxt
- This is the transform context (XML::LibXSLT::TransformContext). You can
use this to get the current XML::LibXSLT::Stylesheet object by calling
"stylesheet()".
my $stylesheet = $tctxt->stylesheet();
The stylesheet object can then be used to share contextual
information between different calls to the security callbacks.
- $value
- This is the name of the resource (file or URI) that has been
requested.
If a particular option (except for
"create_dir") doesn't have a registered
callback, then the stylesheet will have full access for that action.
- new()
- Creates a new XML::LibXSLT::Security object.
- register_callback( $option, $callback )
- Registers a callback function for the given security option (listed
above).
- unregister_callback( $option )
- Removes the callback for the given option. This has the effect of allowing
all access for the given option (except for
"create_dir").
Included in the distribution is a simple benchmark script, which has two drivers
- one for LibXSLT and one for Sablotron. The benchmark requires the testcases
files from the XSLTMark distribution which you can find at
http://www.datapower.com/XSLTMark/
Put the testcases directory in the directory created by this
distribution, and then run:
perl benchmark.pl -h
to get a list of options.
The benchmark requires XML::XPath at the moment, but I hope to
factor that out of the equation fairly soon. It also requires Time::HiRes,
which I could be persuaded to factor out, replacing it with Benchmark.pm,
but I haven't done so yet.
I would love to get drivers for XML::XSLT and XML::Transformiix,
if you would like to contribute them. Also if you get this running on Win32,
I'd love to get a driver for MSXSLT via OLE, to see what we can do against
those Redmond boys!
For debugging purposes, XML::LibXSLT provides version information about the
libxslt C library (but do not confuse it with the version number of
XML::LibXSLT module itself, i.e. with
$XML::LibXSLT::VERSION). XML::LibXSLT issues a warning
if the runtime version of the library is less then the compile-time version.
- XML::LibXSLT::LIBXSLT_VERSION()
- Returns version number of libxslt library which was used to compile
XML::LibXSLT as an integer. For example, for libxslt-1.1.18, it will
return 10118.
- XML::LibXSLT::LIBXSLT_DOTTED_VERSION()
- Returns version number of libxslt library which was used to compile
XML::LibXSLT as a string, e.g. "1.1.18".
- XML::LibXSLT::LIBXSLT_RUNTIME_VERSION()
- Returns version number of libxslt library to which XML::LibXSLT is linked
at runtime (either dynamically or statically). For example, for example,
for libxslt.so.1.1.18, it will return 10118.
- XML::LibXSLT::HAVE_EXLT()
- Returns 1 if the module was compiled with libexslt, 0 otherwise.
This is free software, you may use it and distribute it under the same terms as
Perl itself.
Copyright 2001-2009, AxKit.com Ltd.
Matt Sergeant, matt@sergeant.org
Security callbacks implementation contributed by Shane
Corgatelli.
Petr Pajas , pajas@matfyz.org
Please report bugs via
http://rt.cpan.org/NoAuth/Bugs.html?Dist=XML-LibXSLT
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