|
| Category: |
Web Stuff |
| Author/Contact Info |
Claudio Garcia (gregorovius)
(claudio.garcia@stanfordalumni.org) |
| Description: |
A subclass of LWP::UserAgent that
replicates Netscape's behavior on redirects after a POST
request (ie. it will follow POST
redirects but it will turn them into GETs before doing so
). I believe Microsoft's IE behaves like this as well.
A lot of web applications rely on this
non-standard behavior in browsers so I
think it would
be a good idea to integrate this to LWP.
See Redirect after POST behavior in
LWP::UserAgent differs from Netscape for reference.
Look for the XXX marker in the code to see where this code
differs from the one in LWP::UserAgent. |
package LWP::NetscapeLikeUserAgent;
use LWP::UserAgent;
use vars qw(@ISA);
@ISA = qw(LWP::UserAgent);
#
# request
#
# Substitutes the default (and standard compliant) "request" method of
+ the
# LWP::UserAgent module for one that behaves like the Netscape browser
+, ie.
# it will follow redirects after POST requests.
#
sub request
{
my($self, $request, $arg, $size, $previous) = @_;
LWP::Debug::trace('()');
my $response = $self->simple_request($request, $arg, $size);
my $code = $response->code;
$response->previous($previous) if defined $previous;
LWP::Debug::debug('Simple response: ' .
(HTTP::Status::status_message($code) ||
"Unknown code $code"));
if ($code == &HTTP::Status::RC_MOVED_PERMANENTLY or
$code == &HTTP::Status::RC_MOVED_TEMPORARILY) {
# Make a copy of the request and initialize it with the new URI
my $referral = $request->clone;
# XXX This is where this routine differs from the one in LWP::User
+Agent.
# If the method of the request is POST then we make the method of
+the
# new request be GET, so that it passes the redirect_ok test. This
+ is
# non-standard but is the way Netscape does it, and many web appli
+cations
# rely on this.
if($request->method eq 'POST') {
$referral->method('GET');
$referral->content('');
}
# And then we update the URL based on the Location:-header.
my $referral_uri = $response->header('Location');
{
# Some servers erroneously return a relative URL for redirects
+,
# so make it absolute if it not already is.
local $URI::ABS_ALLOW_RELATIVE_SCHEME = 1;
my $base = $response->base;
$referral_uri = $HTTP::URI_CLASS->new($referral_uri, $base)
->abs($base);
}
$referral->url($referral_uri);
return $response unless $self->redirect_ok($referral);
# Check for loop in the redirects
my $count = 0;
my $r = $response;
while ($r) {
if (++$count > 13 ||
$r->request->url->as_string eq $referral_uri->as_strin
+g) {
$response->header("Client-Warning" =>
"Redirect loop detected");
return $response;
}
$r = $r->previous;
}
return $self->request($referral, $arg, $size, $response);
} elsif ($code == &HTTP::Status::RC_UNAUTHORIZED ||
$code == &HTTP::Status::RC_PROXY_AUTHENTICATION_REQUIRED
)
{
my $proxy = ($code == &HTTP::Status::RC_PROXY_AUTHENTICATION_REQUI
+RED);
my $ch_header = $proxy ? "Proxy-Authenticate" : "WWW-Authenticate
+";
my @challenge = $response->header($ch_header);
unless (@challenge) {
$response->header("Client-Warning" =>
"Missing Authenticate header");
return $response;
}
require HTTP::Headers::Util;
CHALLENGE: for my $challenge (@challenge) {
$challenge =~ tr/,/;/; # "," is used to separate auth-params!
+!
($challenge) = HTTP::Headers::Util::split_header_words($challe
+nge);
my $scheme = lc(shift(@$challenge));
shift(@$challenge); # no value
$challenge = { @$challenge }; # make rest into a hash
for (keys %$challenge) { # make sure all keys are lower
+case
$challenge->{lc $_} = delete $challenge->{$_};
}
unless ($scheme =~ /^([a-z]+(?:-[a-z]+)*)$/) {
$response->header("Client-Warning" =>
"Bad authentication scheme '$scheme'");
return $response;
}
$scheme = $1; # untainted now
my $class = "LWP::Authen::\u$scheme";
$class =~ s/-/_/g;
no strict 'refs';
unless (%{"$class\::"}) {
# try to load it
eval "require $class";
if ($@) {
if ($@ =~ /^Can\'t locate/) {
$response->header("Client-Warning" =>
"Unsupported authentication scheme '$scheme'");
} else {
$response->header("Client-Warning" => $@);
}
next CHALLENGE;
}
}
return $class->authenticate($self, $proxy, $challenge, $respon
+se,
$request, $arg, $size);
}
return $response;
}
return $response;
}
sub redirect_ok
{
1;
}
1;
|
|
•Re: LWP::UserAgent subclass to make it follow redirects after POST (like Netscape)
by merlyn (Sage) on Feb 26, 2002 at 16:15 UTC |
use LWP::UserAgent;
sub LWP::UserAgent::redirect_ok {
my ($self, $request) = @_;
$request->method("GET"),$request->content("") if $request->method eq
+ "POST";
1;
}
...
You can subclass it if you wish, but just "patching" it fixes program-wide
behavior.
-- Randal L. Schwartz, Perl hacker
updated code based on feedback. | [reply]
[d/l] |
|
Doing that is not enough. The POST request must be converted
into a GET request by the agent and its content
removed. That's Netscape's exact behavior, as far as I
remember (I wrote this code about a year ago). This
snippet in my code does it:
if($request->method eq 'POST') {
$referral->method('GET');
$referral->content('');
}
Last time I checked UserAgent was not doing this as a
result of overriding redirect_ok().
Update: This is a reply to Merlyn's original post,
in which redirect_ok simply returned a 1.
| [reply]
[d/l] |
|
The latest LWP::UserAgent allows the behavior of redirect_ok to be
overridden using the requests_redirectable
method.
$ua->requests_redirectable( ); # to read
$ua->requests_redirectable( \@requests ); # to set
This reads or sets the object's list of request names that
$ua->redirect_ok(...) will allow redirection for. By
default, this is ['GET', 'HEAD'], as per RFC 2068. To
change to include 'POST', consider:
push @{ $ua->requests_redirectable }, 'POST';
$ua->redirect_ok($prospective_request)
This method is called by request() before it tries to follow a
redirection to the request in $prospective_request. This should
return a true value if this redirection is permissible.
The default implementation will return FALSE unless the method
is in the object's requests_redirectable list, FALSE if the
proposed redirection is to a "file://..." URL, and TRUE
otherwise.
Subclasses might want to override this.
(This method's behavior in previous versions was simply to return
TRUE for anything except POST requests).
| [reply]
[d/l]
[select] |
¶Re: •Re: LWP::UserAgent subclass to make it follow redirects after POST (like Netscape)
by Anonymous Monk on Feb 27, 2002 at 00:59 UTC |
The latest LWP::UserAgent allows the behavior of redirect_ok to be overridden using the requests_redirectable method.
$ua->requests_redirectable( ); # to read
$ua->requests_redirectable( \@requests ); # to set
This reads or sets the object's list of request names that
$ua->redirect_ok(...) will allow redirection for. By
default, this is ['GET', 'HEAD'], as per RFC 2068. To
change to include 'POST', consider:
push @{ $ua->requests_redirectable }, 'POST';
$ua->redirect_ok($prospective_request)
This method is called by request() before it tries to follow a
redirection to the request in $prospective_request. This should
return a true value if this redirection is permissible.
The default implementation will return FALSE unless the method
is in the object's requests_redirectable list, FALSE if the
proposed redirection is to a "file://..." URL, and TRUE
otherwise.
Subclasses might want to override this.
(This method's behavior in previous versions was simply to return
TRUE for anything except POST requests).
| [reply]
[d/l] |
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