Using SOAP::Lite With Perl
I've been trying to access a SOAP service using Perl for a project, so I took a quick look at CPAN to see what was available. The answer seemed to be to use SOAP::Lite.
This module turned out to be a real devil to use, and my problems with it were probably compounded by my lack of SOAP experience.
SOAP (incase you didn't know) is a method of accessing remote services using XML. In my case, I was trying to access content supplied by a third party ringtone provider using SOAP over HTTP.
Using SOAP::Lite you have to specify a uri and a proxy. What stumped me for a while is that the proxy is the URI of service you wish to access, and uri is the namespace of the service.
So if the provider I was using had their SOAP service available at ws.robstones-services.co.uk/external.asmx, I would use this as the proxy, and in this case I would use ws.robstones-services.co.uk/External as the urinamespace.
Great, I knew the service I needed was called getCallList, and required a Username and Password to be passed to it. In return it would give me a list of valid content types. The SOAPAction header to be added to the call to proxy, letting the remote SOAP service I wanted to use the service http://ws.robstones-services.co.uk/External/getCallList.
My first attempt was the following code...
#!/usr/bin/perl -w
use strict;
use SOAP::Lite 'trace', 'debug';
my $server = SOAP::Lite
->uri('http://ws.robstones-services.co.uk/External')
->proxy('http://ws.robstones-services.co.uk/external.asmx');
my $returned = $server
->getCallList({
'Username' => 'RobsUser',
'Password' => 'RobsPassword'
});
foreach my $type ($returned->valueof('//getCallListResult/string')) {
next unless ($type); ## ignore any undefs
print "$type\n";
}
You'll notice I'm using trace and debug to see the SOAP messages being sent and received. The dialogue from this script was...
> perl -w test.pl
SOAP::Transport::HTTP::Client::send_receive: POST http://ws.robstones-services.co.uk/external.asmx HTTP/1.1
Accept: text/xml
Accept: multipart/*
Content-Length: 615
Content-Type: text/xml; charset=utf-8
SOAPAction: "http://ws.robstones-services.co.uk/External#getCallList"
<?xml version="1.0" encoding="UTF-8"?><SOAP-ENV:Envelope xmlns:xsi="http://www.w3.org/1999/XMLSchema-instance" xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/" xmlns:xsd="http://www.w3.org/1999/XMLSchema" SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"><SOAP-ENV:Body><namesp1:getCallList xmlns:namesp1="http://ws.robstones-services.co.uk/External"><c-gensym3><Username xsi:type="xsd:string">RobsUser</Username><Password xsi:type="xsd:string">RobsPassword</Password></c-gensym3></namesp1:getCallList></SOAP-ENV:Body></SOAP-ENV:Envelope>
SOAP::Transport::HTTP::Client::send_receive: HTTP/1.1 500 (Internal Server Error) Internal Server Error.
Cache-Control: private
Connection: close
Date: Tue, 29 Nov 2005 15:23:38 GMT
Server: Microsoft-IIS/6.0
Content-Length: 508
Content-Type: text/xml; charset=utf-8
Client-Date: Tue, 29 Nov 2005 15:23:09 GMT
Client-Response-Num: 1
X-AspNet-Version: 1.1.4322
X-Powered-By: ASP.NET
<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<soap:Body>
<soap:Fault>
<faultcode>soap:Client</faultcode>
<faultstring>Server did not recognize the value of HTTP Header SOAPAction: http://ws.robstones-services.co.uk/External#getCallList.</faultstring>
<detail />
</soap:Fault>
</soap:Body>
</soap:Envelope>
The call didn't work, you'll see the SOAPAction variable is wrong, it's http://ws.robstones-services.co.uk/External#getCallList instead of http://ws.robstones-services.co.uk/External/getCallList.
I needed to get SOAP::Lite to use the correct URL. The secret turned out to be to change the use SOAP::Lite line to the following.
use SOAP::Lite on_action =*gt; sub {sprintf '%s/%s', @_},
'trace', 'debug';
on_action is a parameter SOAP::Lite uses to separate the URI from the action, here we're telling it to use /.
This gave me the following SOAP dialogue...
> perl -w test.pl
SOAP::Transport::HTTP::Client::send_receive: POST http://ws.robstones-services.co.uk/external.asmx HTTP/1.1
Accept: text/xml
Accept: multipart/*
Content-Length: 615
Content-Type: text/xml; charset=utf-8
SOAPAction: http://ws.robstones-services.co.uk/External/getCallList
<?xml version="1.0" encoding="UTF-8"?><SOAP-ENV:Envelope xmlns:xsi="http://www.w3.org/1999/XMLSchema-instance" xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/" xmlns:xsd="http://www.w3.org/1999/XMLSchema" SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"><SOAP-ENV:Body><namesp1:getCallList xmlns:namesp1="http://ws.robstones-services.co.uk/External"><c-gensym3><Username xsi:type="xsd:string">RobsUser</Username><Password xsi:type="xsd:string">RobsPassword</Password></c-gensym3></namesp1:getCallList></SOAP-ENV:Body></SOAP-ENV:Envelope>
SOAP::Transport::HTTP::Client::send_receive: HTTP/1.1 200 OK
Cache-Control: private, max-age=0
Connection: close
Date: Tue, 29 Nov 2005 15:22:53 GMT
Server: Microsoft-IIS/6.0
Content-Length: 405
Content-Type: text/xml; charset=utf-8
Client-Date: Tue, 29 Nov 2005 15:22:25 GMT
Client-Response-Num: 1
X-AspNet-Version: 1.1.4322
X-Powered-By: ASP.NET
<?xml version="1.0" encoding="utf-8"?><soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"><soap:Body><getCallListResponse xmlns="http://ws.robstones-services.co.uk/External"><getCallListResult><string xsi:nil="true" /></getCallListResult></getCallListResponse></soap:Body></soap:Envelope>
Bugger, it still didn't work. I looked again at the SOAP message being sent. It was sending a lot of namespace information and a wrapper around the Username and Password. The wrapper was definitely wrong, and the remote .NET service didn't seem to like the namespaces.
I needed to sort that out, so I had to tell SOAP::Lite to not to include namespaces or wrap up the Username and Password. The way to do this is to use SOAP::Data to hardcode the data being sent.
This meant changing the call to getCallList to the following...
my $returned = $server
->getCallList(
SOAP::Data->name('Username')->value('RobsUser')->type(''),
SOAP::Data->name('Password')->value('RobsPassword')->type('')
);
The SOAP dialogue after these changes looked like this..
SOAP::Transport::HTTP::Client::send_receive: POST http://ws.robstones-services.co.uk/external.asmx HTTP/1.1
Accept: text/xml
Accept: multipart/*
Content-Length: 548
Content-Type: text/xml; charset=utf-8
SOAPAction: http://ws.robstones-services.co.uk/External/getCallList
<?xml version="1.0" encoding="UTF-8"?><SOAP-ENV:Envelope xmlns:xsi="http://www.w3.org/1999/XMLSchema-instance" xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/" xmlns:xsd="http://www.w3.org/1999/XMLSchema" SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"><SOAP-ENV:Body><namesp1:getCallList xmlns:namesp1="http://ws.robstones-services.co.uk/External"><Username>RobsUser</Username><Password>RobsPassword</Password></namesp1:getCallList></SOAP-ENV:Body></SOAP-ENV:Envelope>
SOAP::Transport::HTTP::Client::send_receive: HTTP/1.1 200 OK
Cache-Control: private, max-age=0
Connection: close
Date: Tue, 29 Nov 2005 15:19:49 GMT
Server: Microsoft-IIS/6.0
Content-Length: 405
Content-Type: text/xml; charset=utf-8
Client-Date: Tue, 29 Nov 2005 15:19:21 GMT
Client-Response-Num: 1
X-AspNet-Version: 1.1.4322
X-Powered-By: ASP.NET
<?xml version="1.0" encoding="utf-8"?><soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"><soap:Body><getCallListResponse xmlns="http://ws.robstones-services.co.uk/External"><getCallListResult><string xsi:nil="true" /></getCallListResult></getCallListResponse></soap:Body></soap:Envelope>
Close, but still not right. The problem was with the getCallList itself, it was still trying to use a namespace.
The final solution was to this problem was to not use getCallList, but instead to use SOAP::Lite's call method to implicitly set how the function was being called.
The code after making this change was the following...
my $returned = $server
->call(SOAP::Data->name('getCallList')->attr({xmlns => 'http://ws.robstones-services.co.uk/External'}) =>
SOAP::Data->name('Username')->value('RobsUser')->type(''),
SOAP::Data->name('Password')->value('RobsPassword')->type('')
);
This gave me the SOAP dialogue...
> perl -w test_soap.pl
SOAP::Transport::HTTP::Client::send_receive: POST http://ws.robstones-services.co.uk/external.asmx HTTP/1.1
Accept: text/xml
Accept: multipart/*
Content-Length: 524
Content-Type: text/xml; charset=utf-8
SOAPAction: http://ws.robstones-services.co.uk/External/getCallList
<?xml version="1.0" encoding="UTF-8"?><SOAP-ENV:Envelope xmlns:xsi="http://www.w3.org/1999/XMLSchema-instance" xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/" xmlns:xsd="http://www.w3.org/1999/XMLSchema" SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"><SOAP-ENV:Body><getCallList xmlns="http://ws.robstones-services.co.uk/External"><Username>RobsUser</Username><Password>RobsPassword</Password></getCallList></SOAP-ENV:Body></SOAP-ENV:Envelope>
SOAP::Transport::HTTP::Client::send_receive: HTTP/1.1 200 OK
Cache-Control: private, max-age=0
Connection: close
Date: Tue, 29 Nov 2005 15:16:07 GMT
Server: Microsoft-IIS/6.0
Content-Length: 540
Content-Type: text/xml; charset=utf-8
Client-Date: Tue, 29 Nov 2005 15:15:39 GMT
Client-Response-Num: 1
X-AspNet-Version: 1.1.4322
X-Powered-By: ASP.NET
<?xml version="1.0" encoding="utf-8"?><soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"><soap:Body><getCallListResponse xmlns="http://ws.robstones-services.co.uk/External"><getCallListResult><string>ROBS_JAVA</string><string>ROBS_WALL</string><string>ROBS_POLY</string><string>ROBS_MONO</string><string>ROBS_REAL</string><string xsi:nil="true" /></getCallListResult></getCallListResponse></soap:Body></soap:Envelope>
ROBS_JAVA
ROBS_WALL
ROBS_POLY
ROBS_MONO
ROBS_REAL
Hurrah, after all that effort, I have a list of 5 types of content offered by my third party supplier. I can now go ahead and build my service.
SOAP::Lite is a powerful module, but the lack of simple, easy to follow documentation and examples holds it back. I hope this small article helps out other programmers just starting on the SOAP path.