HTTP::Headers - Class encapsulating HTTP Message headers
SYNOPSIS
require HTTP::Headers;
$h = new HTTP::Headers;
DESCRIPTION
The HTTP::Headers class encapsulates HTTP-style message
headers. The headers consist of attribute-value pairs,
which may be repeated, and which are printed in a
particular order.
Instances of this class are usually created as member
variables of the HTTP::Request and HTTP::Response classes,
internal to the library.
The following methods are available:
$h = new HTTP::Headers
Constructs a new HTTP::Headers object. You might pass
some initial attribute-value pairs as parameters to
the constructor. E.g.:
$h = new HTTP::Headers
Date => 'Thu, 03 Feb 1994 00:00:00 GMT',
Content_Type => 'text/html; version=3.2',
Content_Base => 'http://www.sn.no/';
$h->header($field [=> $val],...)
Get or set the value of a header. The header field
name is not case sensitive. To make the life easier
for perl users who wants to avoid quoting before the
=> operator, you can use '_' as a synonym for '-' in
header names.
The value argument may be a scalar or a reference to a
list of scalars. If the value argument is not defined,
then the header is not modified.
The header() method accepts multiple ($field =>
$value) pairs.
The list of previous values for the last $field is
returned. Only the first header value is returned in
scalar context.
$header->header(MIME_Version => '1.0',
User_Agent => 'My-Web-Client/0.01');
$header->header(Accept => "text/html, text/plain, image/*");
$header->header(Accept => [qw(text/html text/plain image/*)]);
Apply a subroutine to each header in turn. The
callback routine is called with two parameters; the
name of the field and a single value. If the header
has more than one value, then the routine is called
once for each value. The field name passed to the
callback routine has case as suggested by HTTP Spec,
and the headers will be visited in the recommended
"Good Practice" order.
$h->as_string([$endl])
Return the header fields as a formatted MIME header.
Since it internally uses the scan() method to build
the string, the result will use case as suggested by
HTTP Spec, and it will follow recommended "Good
Practice" of ordering the header fieds. Long header
values are not folded.
The optional parameter specifies the line ending
sequence to use. The default is "\n". Embedded "\n"
characters in the header will be substitued with this
line ending sequence.
$h->push_header($field, $val)
Add a new field value of the specified header. The
header field name is not case sensitive. The field
need not already have a value. Previous values for the
same field are retained. The argument may be a scalar
or a reference to a list of scalars.
$header->push_header(Accept => 'image/jpeg');
$h->remove_header($field,...)
This function removes the headers with the specified
names.
$h->clone
Returns a copy of this HTTP::Headers object.
CONVENIENCE METHODS
The most frequently used headers can also be accessed
through the following convenience methods. These methods
can both be used to read and to set the value of a header.
The header value is set if you pass an argument to the
method. The old header value is always returned.
Methods that deal with dates/times always convert their
value to system time (seconds since Jan 1, 1970) and they
also expect this kind of value when the header value is
set.
$h->date
$h->date(time); # set current date
$h->expires
This header gives the date and time after which the
entity should be considered stale.
$h->if_modified_since
$h->if_unmodified_since
This header is used to make a request conditional. If
the requested resource has not been modified since the
time specified in this field, then the server will
return a "304 Not Modified" response instead of the
document itself.
$h->last_modified
This header indicates the date and time at which the
resource was last modified. E.g.:
# check if document is more than 1 hour old
if ($h->last_modified < time - 60*60) {
...
}
$h->content_type
The Content-Type header field indicates the media type
of the message content. E.g.:
$h->content_type('text/html');
The value returned will be converted to lower case,
and potential parameters will be chopped off and
returned as a separate value if in an array context.
This makes it safe to do the following:
if ($h->content_type eq 'text/html') {
# we enter this place even if the real header value happens to
# be 'TEXT/HTML; version=3.0'
...
}
$h->content_encoding
The Content-Encoding header field is used as a
modifier to the media type. When present, its value
indicates what additional encoding mechanism has been
applied to the resource.
$h->content_length
$h->content_language
The natural language(s) of the intended audience for
the message content. The value is one or more
language tags as defined by RFC 1766. Eg. "no" for
Norwegian and "en-US" for US-English.
$h->title
The title of the document. In libwww-perl this header
will be initialized automatically from the
<TITLE>...</TITLE> element of HTML documents. This
header is no longer part of the HTTP standard.
$h->user_agent
This header field is used in request messages and
contains information about the user agent originating
the request. E.g.:
$h->user_agent('Mozilla/1.2');
$h->server
The server header field contains information about the
software being used by the originating server program
handling the request.
$h->from
This header should contain an Internet e-mail address
for the human user who controls the requesting user
agent. The address should be machine-usable, as
defined by RFC822. E.g.:
$h->from('Gisle Aas <aas@sn.no>');
$h->referer
Used to specify the address (URI) of the document from
which the requested resouce address was obtained.
$h->www_authenticate
This header must be included as part of a "401
Unauthorized" response. The field value consist of a
challenge that indicates the authentication scheme and
parameters applicable to the requested URI.
$h->proxy_authenticate
This header must be included in a "407 Proxy
Authentication Required" response.
$h->authorization
$h->proxy_authorization
headers.
$h->authorization_basic
This method is used to get or set an authorization
header that use the "Basic Authentication Scheme". In
array context it will return two values; the user name
and the password. In scalar context it will return
"uname:password" as a single string value.
When used to set the header value, it expects two
arguments. E.g.:
$h->authorization_basic($uname, $password);
The method will croak if the $uname contains a colon
':'.
$h->proxy_authorization_basic
Same as authorization_basic() but will set the "Proxy-
Authorization" header instead.
COPYRIGHT
Copyright 1995-1997 Gisle Aas.
This library is free software; you can redistribute it
and/or modify it under the same terms as Perl itself.