Using SQL Server Native Web Services

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This week I spent some time implementing an integration-scenario for a client. There were some complicating factors that we managed to overcome, and in case it may have wider applicability, I’ve written up our experiences.

The client has a successful e-commerce solution, and wanted updated information on their customers and their orders available in Dynamics CRM, so that complaints and other service requests could be handled consistently. For this sort of scenario, we would typically use ImportManager Studio, a superb piece if kit from from CRM Extensions. Given an ODBC connection to a data source and access to the CRM web service, it will merrily integrate data to almost all parts of the CRM data model.

Unfortunately, the e-commerce database was not hosted at the client’s premises. A rickety VPN-line was available, but deemed unsuitable and the hosting company was unwilling to open port 1433 directly to the SQL-server — a reasonable stand. We decided that a web service extracting information from the database and deployed somewhere on the e-commerce website would provide a solution acceptable to all, and I set to work.

First up, I wrote stored procedures to extract the required data. The database layout was very… different, but the forces of good prevailed. Next up was the implementation of the web services themselves. The group architect was assigned to the project, and figuring I had better do it right, I set about creating business-entity classes with associated data-accessors. This involved lots of tedious copy-paste boilerplate-coding but after a while, I was serving out tidy XML:

<ArrayOfOrder>
    <Order>
        <OrderNum>123</OrderNum>
        <OrderDate>03-08-2007</OrderDate>
        .
        .
        .
        <OrderLines>
            <OrderLine>
                <Linenr>1</Linenr>
                <Productcode>321</Productcode>
                .
                .
                .
            </OrderLine>
        </OrderLines>
    </Order>
</ArrayOfOrder>

Before moving onto the customers, I paused and looked at the code. While I was happy with the output, the associated effort and complexity seemed excessive. Indeed, each order-attribute exposed through the web service was named, renamed, referenced or manhandled in some other way no less than 10 times: twice in the stored procedure, twice in the data-access class, twice again in the entity-class constructor and four times around the property with associated getters and setters. While Visual Studio or SQL Server checked the validity of most af these occurrences (and their number can be significantly reduced in .Net 3.5), several where just free-floating strings. Worse, there was the risk of similar-looking attributes being cross-assigned due to some cut-‘n-paste error — I had found several of these already. Further, if the customer decided they needed more attributes migrated, adding them would be significant hassle.

Leaning back, unhappy with this state of affairs, I tried to come up with better, simpler solution. It was then I remembered something about SQL Server having it’s own web service thingamabob, and — after some bumbling around — lo and behold: Native XML Web Services for Microsoft SQL Server 2005. The introduction has it pretty well:

Microsoft SQL Server 2005 provides a standard mechanism for accessing the database engine using SOAP via HTTP. Using this mechanism, you can send SOAP/HTTP requests to SQL Server to execute:

  • Transact-SQL batch statements, with or without parameters.
  • Stored procedures, extended stored procedures, and scalar-valued user-defined functions.

Neat huh? SQL Server seems to accomplish this feat by registering itself directly with the OS(through http.sys), independent of any IIS, ensuring that relevant requests comes its way. The documentation on the “create endpoint” statement is terse and I couldn’t find any non-trivial examples. After some trying, I managed to concoct a statement palatable to the sophisticated tastes of SQL Server:

create endpoint Orders
	state = started
as http
(
	path='/sql/orders',
	authentication = (integrated),
	ports = (clear),
	clear_port = 8080,
	site = 'db-server'
)
for soap
(
	webmethod 'GetOrdersModifiedAfter'
		(name = 'Orderdb.dbo.GetOrdersModifiedAfter'),
	batches = disabled,
	wsdl = default,
	database = 'Orderdb',
	namespace = 'foospace',
	schema = standard
)

Obviously these web services can only be made accessible from the server running SQL Server (i.e. deploying them to the web-server running the e-commerce stuff was not an option). So — having validated the approach — I had to check with the hosting guys that it was OK to poke a hole in the firewall to the SQL server on port 8080. Security for this approach should be solid: Requests are authenticated at the http-level before being checked again by SQL Server. As a further measure at the host-site, only requests from the CRM-server IP are allowed through the firewall.

The downside to this approach was that my web service now disgorged object-arrays containing ADO DataSets (that is, if you’ve been a good boy…). The slightly added complexity in the code interacting with the web service was well worth the elimination of the entire middle tier on the database-end though. The DataSet can be found with this code (more than one may be returned, so watch out):

private static DataSet GetDataSet(object[] objectArray)
{
	DataSet ds = null;
	foreach (object o in objectArray)
	{
		if (o.GetType().ToString() == "System.Data.DataSet")
		{
			ds = (DataSet)o;
		}
	}
	return ds;
}

So there you have it: Found a off-site SQL Server with interesting data to be had? Native Web Services provides quick and low-maintenance access to it.

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