XML Integration with ADO - Saving Recordsets as XML

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Using ADO we can very easily generate XML recordsets by making use of  “Save” method of the Recordset object, and specifying the format as “adPersistXML”. This feature isn’t new to ADO 2.5, but what is novel is the ability to persist hierarchical recordsets, and to directly persist them into other objects, such as DOM objects and streams.

This opens up any number of possibilities for manipulation and transfer of data, since we are no longer restricted to creating text files containing XML data. Why is this such good news? Well, as programmers we want two major things to work without hassle:

• An easy way to generate data.
• A fast way to transfer data.

Creating text files is easy, but slow. It involves tedious work like writing the file to the disk, and then reading the data back in to manipulate it. What we are trying to reach ultimately is finding out ways to eliminate as much as the slow processing as possible. If we could derive at anything that makes our life easier as programmer or developers has to be good thing.

Persisting ADO Recordsets to XML Files

The simplest method of converting ADO recordset to XML is a method that’s been in previous version of ADO. Just included this code for reference.

<pre><blockquote><font face=verdana size=1>
rs.Authors.Save  “c:tempauthors.xml”
</font></blockquote></pre>

Persisting ADO Recordsets to a Stream

A Stream is simply a block of data in memory, which is not processed in any way. ADO 2.5 introduced the new Stream object, and this can be the way for saving a recordset.


Set rsAuthors = Server.CreateObject(ADOBD.Recordset”);
Set stmAuthors = Server.CreateObject(ADOBD.Stream”);
rsAuthors.Open “authors”, strConn
rsAuthors.Save  stmAuthors, adpersistXML



We now have a Stream object containing the XML recordset, and we can use the stream methods and properties to manipulate data. Let’s say we want to extract the XML into a string using the ReadText method, we could do so as follows:


strXMLAuthors = stmAuthors.ReadText.



At this stage strXMLAuthors contains the complete XML recordset including the schema.

Persisting ADO Recordsets to the Response Object

We can think of streams as something more literal. The dictionary defines a stream as "a flow or moving succession of anything." So, let's think of a stream of data as a flow of data from one place to another. Keeping this in mind, let’s imagine we are sending this data from our ASP page to browser-that’s a flow of data, too.

Just how do we do this?  We do so by using a new feature of the Response object, which has built in support for Streams. So it is like pouring our data into one end of the stream, and having it end up at the other end. On one end is the Response Object, and the other end is the browser. All this is made feasible because of the integrated support for streams in the Response object:


rsAuthors.Save Response, adPersistXML



This saves the recordset as XML directly into the response object. The Response object in turn handles the sending of data to the browser. Pretty cool!

Conclusion

Today we have learned about:

1. binding hierarchical XML data, such as those in data shaped recordsets
2. enumerated the working of XML data with Data Island
3. persisting ADO recordsets to XML files as well as streams
4. a easier way of Persisting ADO recordsets to Response objects.

Each one has its own advantages over the other. But there is a much easier way to do this, which is Persisting ADO Recordsets to DOM object, which we will be covering in depth in the next part of the tutorial.

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