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Bringing SOAP to Flash 5
Author: Tom Van den Eynde
| Website: http://www.carels.com |
Bringing SOAP to Flash 5
The problem
Flash 5 has support for XML communications over HTTP. However, sadly enough,
there is no support for setting HTTP headers.
The 'SOAPAction' HTTP header is however essential if you want to communicate
with SOAP-compliant webservices.
And what is very popular these days ? Yes, SOAP-based webservices...
And why are they popular ? Because they allow you to access business logic
functionalities (for example doing a query to retrieve flight availability or
the wheather in your city or live stock quotes or ...) over the Internet in a
structured form (in other words without having to do screen- or HTML- scraping).
Do you, as a Flash developer, want to have access to these functionalities
(check out http://uddi.microsoft.com for
an overview of some of the webservices available to you today) ?
I do ! In order to make it possible for our
Carels.Visual Studio tool
(which allows you to build rich, web-enabled, user interfaces for business
applications) to
communicate with SOAP-compliant webservices I had to come up with a solution.
A possible solution
The solution is based on an ASP script but could be implemented using a Java
servlet as well.
The idea is to send the XML request to this script. The script then adds, using
information passed through the URL, the necessary SOAP elements in order to make
the request SOAP-compliant.
An example of what a SOAP request and response looks like can be found at :
http://www22.brinkster.com/prasads/LiveQuoteService.asmx
SOAPAction HTTP-header issue
The major issue is the SOAPAction HTTP-header. It is just not possible to set
such headers through Flash 5. Specificying the URL and the SOAPAction as
variables in the URL used to call the ASP script makes it possible for the ASP
script to use this information in order to build the required SOAP-compliant
request.
Use the following URL construction (this solution only works with the POST
method, NOT with the GET method !) :
http://HostnameOfAspHost/SomeVirtualDirectory/adsoap.asp?URL=http://HostnameOfSoapHost/SomeWebserviceUrl&SOAPAction=TheSoapActionRequired
SOAP envelop and body issue
Another, but minor, issue is the SOAP envelope and body. Support has been
foreseen in the script for automatically adding the SOAP envelope and body can
be done by adding the variable 'Envelope' to the URL. This variables has 3
possible values :
1 : Add the envelope and body to the outgoing XML
2 : Add the envelope and body to the outgoing XML and remove the envelope and
body from the incoming XML
3 : Remove the envelope and body from the incoming XML
http://HostnameOfAspHost/SomeVirtualDirectory/adsoap.asp?URL=http://HostnameOfSoapHost/SomeWebserviceUrl&SOAPAction=TheSoapActionRequired&Envelope=2
When automatically adding the SOAP envelope and body (by specifying 1 or 2
for the Envelope variable) you can optionally set the encoding
attribute of the XML processing instruction. This can be achieved by specifying
the 'Encoding' variable on the URL :
http://HostnameOfAspHost/SomeVirtualDirectory/adsoap.asp?URL=http://HostnameOfSoapHost/SomeWebserviceUrl&SOAPAction=TheSoapActionRequired&Envelope=2&Encoding=iso-8859-1">http://HostnameOfAspHost/SomeVirtualDirectory/adsoap.asp?URL=http://HostnameOfSoapHost/SomeWebserviceUrl&SOAPAction=TheSoapActionRequired&Envelope=2&Encoding=iso-8859-1
The application domain issue
If you have been playing around with the XML over HTTP communication support
in Flash then you are probably aware that it doesn't allow you to communicate
outside your application domain. In other words hostnames different from the
hostname used
to access your Flash movie don't work.
This script solves this issue as well as it routes your call via the ASP script living next to your Flash movie. The ASP script doesn't suffer from the application domain limitation.
| » Level Intermediate |
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Added: : 2002-01-24
Rating: 6.45 Votes: 11
Hits: 4070
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| » Author |
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Tom Van den Eynde is Product Marketing Director at Carels Corporation. Tom promotes the usage of XML and web services, not only for use in B2B and B2C scenarios but also as a means to build better user interfaces for business applications, portals, ... In the past he has developed thin client solutions that are being used by major companies worldwide.
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