[Chapter 17] 17.4 The HTML Module
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[Chapter 17] 17.4 The HTML Module
q
eof
When the parse or parse_file method is called, it parses the incoming HTML with a few internal methods.
In HTML::Parser, these methods are defined, but empty. Additional HTML parsing classes (included in the
HTML modules or ones you write yourself) override these methods for their own purposes. For example:
package HTML::MyParser;
require HTML::Parser;
@ISA=qw(HTML::MyParser);
sub start {
your subroutine defined here
}
The following list shows the internal methods contained in HTML::Parser:
q comment
q
declaration
q
end
q
start
q
text
17.4.2 HTML::Element
The HTML::Element module provides methods for dealing with nodes in an HTML syntax tree. You can get or
set the contents of each node, traverse the tree, and delete a node.
HTML::Element objects are used to represent elements of HTML. These elements include start and end tags,
attributes, contained plain text, and other nested elements.
The constructor for this class requires the name of the tag for its first argument. You may optionally specify initial
attributes and values as hash elements in the constructor. For example:
$h = HTML::Element->new('a', 'href' => 'http://www.oreilly.com');
The new element is created for the anchor tag, , which links to the URL through its href attribute.
The following methods are provided for objects of the HTML::Element class:
q as_HTML
q
attr
q
content
q
delete
q
delete_content
q
dump
q
endtag
q
extract_links
q
implicit
q
insert_element
q
is_empty
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[Chapter 17] 17.4 The HTML Module
q
is_inside
q
parent
q
pos
q
push_content
q
starttag
q
tag
q
traverse
17.4.3 HTML::TreeBuilder
The HTML::TreeBuilder class provides a parser that creates an HTML syntax tree. Each node of the tree is an
HTML::Element object. This class inherits both HTML::Parser and HTML::Elements, so methods from both of
those classes can be used on its objects.
The methods provided by HTML::TreeBuilder control how the parsing is performed. Values for these methods
are set by providing a boolean value for their arguments. Here are the methods:
q implicit_tags
q
ignore_unknown
q
ignore_text
q
warn
17.4.4 HTML::FormatPS
The HTML::FormatPS module converts an HTML parse tree into PostScript. The formatter object is created with
the new constructor, which can take parameters that assign PostScript attributes. For example:
$formatter = new HTML::FormatPS('papersize' => 'Letter');
You can now give parsed HTML to the formatter and produce PostScript output for printing. HTML::FormatPS
does not handle table or form elements at this time.
The method for this class is format. format takes a reference to an HTML TreeBuilder object, representing a
parsed HTML document. It returns a scalar containing the document formatted in PostScript. The following
example shows how to use this module to print a file in PostScript:
use HTML::FormatPS;
$html = HTML::TreeBuilder->parse_file(somefile);
$formatter = new HTML::FormatPS;
print $formatter->format($html);
The following list describes the attributes that can be set in the constructor:
PaperSize
Possible values of 3, A4, A5, B4, B5, Letter, Legal, Executive, Tabloid, Statement, Folio, 10x14, and
Quarto. The default is A4.
PaperWidth
Width of the paper in points.
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[Chapter 17] 17.4 The HTML Module
PaperHeight
Height of the paper in points.
LeftMargin
Left margin in points.
RightMargin
Right margin in points.
HorizontalMargin
Left and right margin. Default is 4 cm.
TopMargin
Top margin in points.
BottomMargin
Bottom margin in points.
VerticalMargin
Top and bottom margin. Default is 2 cm.
PageNo
Boolean value to display page numbers. Default is 0 (off).
FontFamily
Font family to use on the page. Possible values are Courier, Helvetica, and Times. Default is Times.
FontScale
Scale factor for the font.
Leading
Space between lines, as a factor of the font size. Default is 0.1.
17.4.5 HTML::FormatText
The HTML::FormatText takes a parsed HTML file and outputs a plain text version of it. None of the character
attributes will be usable, i.e., bold or italic fonts, font sizes, etc.
This module is similar to FormatPS in that the constructor takes attributes for formatting, and the format
method produces the output. A formatter object can be constructed like this:
$formatter = new HTML::FormatText (leftmargin => 10, rightmargin => 80);
The constructor can take two parameters: leftmargin and rightmargin. The value for the margins is given
in column numbers. The aliases lm and rm can also be used.
The format method takes an HTML::TreeBuilder object and returns a scalar containing the formatted text. You
can print it with:
print $formatter->format($html);
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[Chapter 17] 17.4 The HTML Module
17.3 The HTTP Modules
17.5 The URI Module
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[Chapter 17] 17.5 The URI Module
Chapter 17
The LWP Library
17.5 The URI Module
The URI module contains functions and modules to specify and convert URIs. (URLs are a type of URI.)
There are three URI modules: URL, Escape, and Heuristic. Of primary importance to many LWP
applications is the URI::URL class, which creates the objects used by LWP::UserAgent to determine
protocols, server locations, and resource names.
The URI::Escape module replaces unsafe characters in URL strings with their appropriate escape
sequences. URI::Heuristic provides convenience methods for creating proper URLs out of short strings
and incomplete addresses.
17.5.1 URI::Escape
This module escapes or unescapes "unsafe" characters within a URL string. Unsafe characters in URLs
are described by RFC 1738. Before you form URI::URL objects and use that class's methods, you should
make sure your strings are properly escaped. This module does not create its own objects; it exports the
following functions:
q uri_escape
q
uri_unescape
17.5.2 URI::URL
This module creates URL objects that store all the elements of a URL. These objects are used by the
request method of LWP::UserAgent for server addresses, port numbers, file names, protocol, and
many of the other elements that can be loaded into a URL.
The new constructor is used to make a URI::URL object:
$url = new URI::URL($url_string [, $base_url])
This method creates a new URI::URL object with the URL given as the first parameter. An optional base
URL can be specified as the second parameter and is useful for generating an absolute URL from a
relative URL.
The following list describes the methods for the URI::URL class:
q abs
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[Chapter 17] 17.5 The URI Module
q
as_string
q
base
q
crack
q
default_port
q
eparams
q
epath
q
eq
q
equery
q
frag
q
full_path
q
host
q
netloc
q
params
q
password
q
path
q
port
q
query
q
rel
q
scheme
q
strict
q
user
17.4 The HTML Module
VII. Perl/Tk
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