Yossi Dahan [BizTalk]


Thursday, September 06, 2007

Unnecessary limitation when using custom proxy for web services in BizTalk 2006

We're using a third party web service quite extensively; sometimes the size of messages exchanged between us can be quite big, which is not ideal from a performance point of view.

Luckily - they are quire advanced and mature and have a good support for compressed messages exchange.

To use that we needed to compress the stream going out over the wire through the adapter and set the Content-Encoding HTTP header to "gzip" to indicate the stream is compressed, on their end, if the header is set that way, they would decompress the stream before processing the message , and will compress the response in a similar way.

They were even kind enough to provide us with a class that enhances System.Web.Services.Protocols.SoapHttpClientProtocol (through inheritance) to do all of that, so really - all we needed to do to use their web service in our playground windows application was to change the proxy class generated by Visual Studio when we added the web reference to inherit from their class rather than SoapHttpClientProtocol (their class would ultimately ingerit from SoapHttpClientProtocol).

We've played with it for a while and it worked great, which meant we were ready to move it from our playground application to our BizTalk implementation; As you can guess by the fact I'm bothering with this post - it didn't go smooth…

I've played with custom web service proxies before - generated a proxy from a WSDL and configured the port to use it - so I knew that in general principle that works quite nicely;

And so I went on and generated a proxy class for that web service and changed the inheritance to the class they've provided.

When I tried to select it in the Admin Console as the proxy class to use, I could browse to the assembly I've built but, once selected, I would get the following error:

This did not make sense to me - the proxy I generated inherits from their class which, as I have the source code, I'm sure inherits from SoapHttpClientProtocol. This error did not make sense to me.

Trying to figure this one out I went on to create my own class ("TestClass") that inherits from SoapHttpClientProtocol (and had not other implementation otherwise) and changed the generated proxy to inherit from that - so basically I created the same scenario - proxy inherits from class inherits from SoapHttpClientProtocol.

When I tried to select my updated assembly in the admin console I could not select the original proxy (now inheriting from TestClass), I could, however, select TestClass itself (which inherits directly from SoapHttpClientProtocol ) but only to get another error -

This error was quickly solved by adding a public web method to TestClass; now TestClass could be selected in the UI, my proxy class, however, the one I really needed, that does not inherit directly from SoapHttpClientProtocol, could not be selected.

It has also solved the mistery, or so I I believe - it seems the UI will only display classes whose base type is SoapHttpClientProtocol, when it should havem in my view, displayed all classes whose IsSubclassOf(typeof(SoapHttpClientProtocol)) is true.

For us the solution was simple - we took all the code we were kindly given from the 3rd party and merged it into our proxy class which could then be left to inherit directly from SoapHttpClientProtocol . The problem is that this is quite limiting - there's no real scope for re-use and for no good reason.

In fact - I suspect this is just a design time problem, of the kind we spotted quite often recently where the runtime would actually work with something, but you have no way of configuring BizTalk to use it.

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  • Yossi,

    We have a similar requirement to sent a message over http, compressed as gzip and Content-Encoding in the Http header set to 'gzip'. We'll be using a pipeline component to gzip the file, but I cant see any property in the Http adapter for Content-Encoding that I set to 'gzip', tell us how did you set the Content-Encoding in the Http header?


    By Blogger Unknown, at 12/01/2008, 11:11  

  • Hi Sajid, and apologies for the late reply. I hope you'll still get this.

    As I've mentioned in my post we've resorted to developing a custom proxy class for our gzip-web-service, so we've been setting the Content-Encoding http header to GZIP in the proxy's GetWebRequest method (the WebRequest class used has a Headers collection you can add items to.)

    By Blogger Yossi Dahan, at 17/01/2008, 23:02  

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