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lib::HTTP::Headers

Section: User Contributed Perl Documentation (3)
Updated: libwww-perl-5.48
Index

NAME

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 theHTTP::Request and HTTP::Response classes, internal to thelibrary.

The following methods are available:

$h = new HTTP::Headers

Constructs a new HTTP::Headers object. You might pass some initialattribute-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 [=> $value],...)

Get or set the value of a header. The header field name is not casesensitive. To make the life easier for perl users who wants to avoidquoting before the => operator, you can use `_' as a synonym for `-'in header names (this behaviour can be suppressed by setting$HTTP::Headers::TRANSLATE_UNDERSCORE to a FALSE value).

The header() method accepts multiple ($field => $value) pairs, so youcan update several fields with a single invocation.

The optional $value argument may be a scalar or a reference to a listof scalars. If the $value argument is undefined or not given, then theheader is not modified.

The old value of the last of the $field values is returned.Multi-valued fields will be concatenated with ``,'' as separator inscalar 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/*)]); @accepts = $header->header('Accept');

$h->scan(\&doit)

Apply a subroutine to each header in turn. The callback routine iscalled 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 oncefor each value. The field name passed to the callback routine hascase as suggested by HTTP Spec, and the headers will be visited in therecommended ``Good Practice'' order.

$h->as_string([$endl])

Return the header fields as a formatted MIME header. Since itinternally uses the scan() method to build the string, the resultwill use case as suggested by HTTP Spec, and it will followrecommended ``Good Practice'' of ordering the header fieds. Long headervalues are not folded.

The optional parameter specifies the line ending sequence to use. Thedefault is "\n". Embedded ``\n'' characters in the header will besubstitued with this line ending sequence.

$h->push_header($field, $val)

Add a new field value of the specified header. The header field nameis not case sensitive. The field need not already have avalue. Previous values for the same field are retained. The argumentmay 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 thefollowing convenience methods. These methods can both be used to readand to set the value of a header. The header value is set if you passan argument to the method. The old header value is always returned.

Methods that deal with dates/times always convert their value to systemtime (seconds since Jan 1, 1970) and they also expect this kind ofvalue when the header value is set.

$h->date

This header represents the date and time at which the message wasoriginated. E.g.:

  $h->date(time);  # set current date

$h->expires

This header gives the date and time after which the entity should beconsidered stale.

$h->if_modified_since

$h->if_unmodified_since

This header is used to make a request conditional. If the requestedresource has (not) been modified since the time specified in this field,then the server will return a "304 Not Modified" response instead ofthe document itself.

$h->last_modified

This header indicates the date and time at which the resource was lastmodified. 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 messagecontent. E.g.:

  $h->content_type('text/html');

The value returned will be converted to lower case, and potentialparameters will be chopped off and returned as a separate value if inan 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 themedia type. When present, its value indicates what additionalencoding mechanism has been applied to the resource.

$h->content_length

A decimal number indicating the size in bytes of the message content.

$h->content_language

The natural language(s) of the intended audience for the messagecontent. The value is one or more language tags as defined by RFC1766. Eg. ``no'' for Norwegian and ``en-US'' for US-English.

$h->title

The title of the document. In libwww-perl this header will beinitialized automatically from the <TITLE>...</TITLE> elementof HTML documents. This header is no longer part of the HTTPstandard.

$h->user_agent

This header field is used in request messages and contains informationabout 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 beingused by the originating server program handling the request.

$h->from

This header should contain an Internet e-mail address for the humanuser who controls the requesting user agent. The address should bemachine-usable, as defined by RFC822. E.g.:

  $h->from('Gisle Aas <aasAATTsn.no>');

$h->referer

Used to specify the address (URI) of the document from which therequested 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 theauthentication 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

A user agent that wishes to authenticate itself with a server or aproxy, may do so by including these 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 twovalues; the user name and the password. In scalar context it willreturn "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

This library is free software; you can redistribute it and/ormodify it under the same terms as Perl itself.

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