XML::Compile::SOAP::FAQ(3) frequently asked questions

DESCRIPTION

On this page, a wild collection of questions are answered related to the XML::Compile::SOAP modules. Or better said: let's hope there will be more in the future. If you have contributions either in question or as answer, then please contribute via the xml mailinglist.

Also read XML::Compile::FAQ.

Modifing the messages

add XML header fields

Although WSDLs offer a nice way to define header-fields explicitly, quite a number of applications require fields which are not described. Also some W3C standards play this game. See XML::Compile::SOAP::WSA for a complex example. A simple example follows here. 

  use warnings;
  use strict;
  package XML::Compile::SOAP::MYEXT;
  use base 'XML::Compile::SOAP::Extension';
  use Log::Report;
  use XML::Compile::SOAP::Util      qw/WSDL11/;
  use XML::Compile::Util            qw/pack_type/;
  my $my_ns = 'http://..../';
  my $my_schema_fie = 'aaa.xsd';
  sub wsdl11Init($@)
  {   my ($self, $wsdl, $args) = @_;
      $wsdl->addPrefixes(myprefix => $my_ns);
      $wsdl->importDefinitions($my_schema_file);
      $self;
  }
  sub soap11Operation$$)
  {   my ($self, $op, $args) = @_;
      # towards the server
      $op->addHeader(INPUT
        => "myprefix_$fieldname" => "{$my_ns}$fieldtype");
      # in server answers
      $op->addHeader(OUTPUT => ...);
  }

With "soap11ClientWrapper()" and "soap11HandlerWrapper()" you can influence the client respectively server processing, for instance to fill-in default values.

adding HTTP headers

Some applications require to add headers to the HTTP headers sent or check headers which are received. SOAP is not about HTTP, so you have to dive deeper in the underlaying constructs; you have to construct the code references in more steps, not using the auto-generation mechanisms of some objects, by default hidden to you.

Examples of needs: authentication/cookies in the header, content (crypt) checksums, non-standard content-type headers.

The ::WSDL11 module detects that the soap-http protocol is needed. (There is also a pure http protocol defined in the SOAP spec, which is never used). When the operation gets compiled (with compileClient), the ::SOAPHTTP module is used to create the soap-http specific message transport logic. Then, that module uses LWP to do the actual HTTP exchange. To be able to access the in- and outgoing messages, you have to reach to that LWP::UserAgent.

Michael Ludwig contributed the following example (slightly adapted) Of course, select your own preferences carefully. 

  my $ua = LWP::UserAgent->new(timeout => 10);
  # First the HTTP logic
  # defaults when https is used
  $ua->ssl_opts(verify_hostname => 0, keep_alive => 1);
  # Auto-use cookies
  $ua->cookie_jar( {file => $my_jar_file
    , autosave => 1, ignore_discard => 1 });
  # Now, we need the SOAP logic
  my $trans = XML::Compile::Transport::SOAPHTTP
    ->new(user_agent => $ua, address => $srv_url);
  # Finally the message, with explicit transporter
  my $call = $wsdl->compileClient($opname, transport => $trans);
  # Or more operations at the same time
  # $wsdl->compileCalls(transport => $trans);
  # $answer is the decoded XML content.
  my($answer, $trace) = $call->( \%parms );
  # If you need headers from the response HTTP headers.
  my $http_response = $trace->response;
  print $http_response->header('X-Secret');

You may know the $srv_url to get the address of the server, but you can also ask the operation itself. Here a different implementation: 

  my $op    = $wsdl->operation($opname);
  my $srv   = ($op->addresses)[0];
  my $trans = XML::Compile::Transport::SOAPHTTP->new(address => $srv
    , timeout => 15, ssl_opts => { verify_hostname => 0 });
  # Now configure the userAgent
  my $ua    = $trans->userAgent;
  ...
  my $call  = $op->compileClient(transport => $trans);
  ...

The LWP::UserAgent has many useful hooks (<i>Handlers</i>), for instance "request_send" and "response_done".

Even shorter, The next works as well. In the whole XML::Compile::SOAP suite, parameters passed on higher levels are passed to all lower levels. Yeh, unclean programming but useful. 

  my $ua    = $trans->userAgent;
  my $call  = $wsdl->compileClient(transport => $trans
    , user_agent => $ua);

When you only need to add simple authentication to the headers, you may use the magic of LWP: provide your server address into 

  http://user:[email protected]/service

add Basic Auth HTTP header

An simple example for the previous section, is the often needed basic authentication. You need something like this: 

   my $ua = LWP::UserAgent->new(timeout => 10);
   my $call = $wsdl->compileClient($operation, user_agent => $ua
    , transport_hook => \&basic_auth);
   sub basic_auth($$)
   {   my ($request, $trace) = @_;
       $request->authorization_basic($user, $password);
       $ua->request($request);     # returns $response
   }

That's all. When you use XML::Compile::Cache to maintain the calls (advised), it would look like this: 

   $wsdl->compileCalls(user_agent => $ua, transport_hook => \&basic_auth);

Collection XSD imports

From a maintenance point of view, it is a very bad idea that some XML client implementations load all the required schemas on the moment they start off. The server may change the schemas at any moment, which may break the application at any moment. Also, network problems will cause the application to break easily. Therefore, XML::Compile requires the schemas to be on local disk (although you can use tricks with wget at start-up time to voluntarily give-up your stability)

To collect the imported schema files, you may use this (on the UNIX/Linux prompt) 

  wget -c -nv $(cat * |
                sed -n 's/.*schemaLocation="\([^"]*\)".*/\1/p' |
                sort -u)

In your program, you typically start with 

  my $wsdl = XML::Compile::WSDL11->new($wsdl_filename);
  $wsdl->importDefinitions([glob "*.xsd"]);

Using SSL

Abeltje contributed an SSL usage example, which then got adapted to this: 

   use LWP::UserAgent;
   my $wsdl = XML::Compile::WSDL11->new($wsdlfn);
   # LWP 6.00 introduces ssl_opts
   @ENV{keys %lwp5_ssl} = values %lwp5_ssl
       if LWP::UserAgent->VERSION < 6;
   my $ua = LWP::UserAgent->new(ssl_opts => \%lwp6_ssl);
   $wsdl->compileCalls(user_agent => $ua);

Do not forget to explicitly install "LWP::Protocol::https" !!!

LICENSE

Copyrights 2007-2016 by [Mark Overmeer]. For other contributors see ChangeLog.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. See http://www.perl.com/perl/misc/Artistic.html

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