HTTP::Headers - Class encapsulating
HTTP Message headers
require HTTP::Headers;
$request = new HTTP::Headers;
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.
Constructs a new HTTP::Headers
object. You might pass some initial attribute-value pairs as parameters to
the constructor. E.g.:
$h = new HTTP::Headers
Date => 'Thu, 03 Feb 1994 00:00:00 GMT',
Content_Type => 'text/html; version=3.2',
Content_Base => 'http://www.sn.no/';
Get or set the value of a header. The header field name is not case
sensitive. To make the life easier for perl users who wants to avoid
quoting before the => operator, you can use '_' as a synonym for '-' in
header names.
The value argument may be a scalar or a reference to a list of scalars. If
the value argument is not defined, then the header is not modified.
The header()
method accepts multiple ($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/*)]);
@accepts = $header->header('Accept');
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.
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.
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');
This function removes the headers with the specified names.
Returns a copy of this HTTP::Headers object.
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.
This header represents the date and time at which the message was
originated. E.g.:
$h->date(time); # set current date
This header gives the date and time after which the entity should be
considered stale.
This header is used to make a request conditional. If the requested
resource has not been modified since the time specified in this field, then
the server will return a "304 Not Modified"
response instead of the document itself.
This header indicates the date and time at which the resource was last
modified. E.g.:
# check if document is more than 1 hour old
if ($h->last_modified < time - 60*60) {
...
}
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'
...
}
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.
A decimal number indicating the size in bytes of the
message content.
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.
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');
The server header field contains information about the software being used
by the originating server program handling the request.
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>');
Used to specify the address
(URI) of the document from which the requested resouce
address was obtained.
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.
A user agent that wishes to authenticate itself with a
server, may do so by including this header.
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);