Copying Children From One ColdFusion XML Document To Another

Posted May 14, 2007 at 8:37 AM

Tags: ColdFusion

The other day, Matthew Abbott had contacted me to ask about some advanced JDOM libraries. I have not used JDOM directly in any way so I couldn't really help him. But this got me thinking about XML in general but more specifically, about XML in ColdFusion. I just don't use it that often and certainly, I don't do anything cool with it. So, I thought I would take this opportunity to try some cool stuff.

For this experimentation, I have created two XML document objects: xmlDate and xmlGirls. The xmlDate XML document outlines the agenda for a hot date (who doesn't love pizza and a movie???). The xmlGirls XML document is an XML database of girls:

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CFDumping out the xmlDate XML document, we get:

CFDumping out the xmlGirls XML document, we get:

Now, our XML document about the date has the girl's ID, but that doesn't really help us out much. What we want to do is copy the properties of the girl from the xmlGirls document to the Girl node of the xmlDate document. My first thought about this was, no problem, just use the AddAll() method for the child nodes collection:

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The problem is that when you run the above code, you get the following ColdFusion error:

WRONG_DOCUMENT_ERR: A node is used in a different document than the one that created it.

The issue, which I had never thought about, was that each Node of an XML document is owned by that document. You can't just use a single XML node in two different places and especially NOT in two different XML documents (just as I can't be both at work and at the movies at the same time!!!).

So, how do we get around this? We have to import the girl node into our xmlDate document before we try and insert it somewhere into our xmlDate XML document object model. To help accomplish this, I have come up with a ColdFusion user defined function, XmlAppend(). This UDF takes two XML nodes from two different XML documents (one from each) and then appends the child nodes of the latter to the child nodes of the former:

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Once we have this nifty ColdFusion XML UDF, we can easily copy the girl properties from the xmlGirls document to the xmlDate document:

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Once the node is copied, our resultant xmlDate XML document looks like this:

The girl properties of Girl ID 4 copies over quite nicely. This is some very interesting stuff. It gives me all sorts of ideas about building xml documents in pieces and then easily joining them together to make a bigger, better document (like denormalizing a database).

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Reader Comments

Wow! This is a pretty impressive technique.

Do you know where documentation exists that talks about these built-in functions within the XML document object? I've only ever been familiar with the functions in the CF documentation, which aren't nearly this powerful.

Thanks in advance,
Toby

@Toby,

Take a look at this:

http://java.sun.com/j2se/1.4.2/docs/api/org/w3c/dom/Node.html

It covers the w3c.org java DOM stuff. It seems that ColdFusion is wrapping around that functionality.

Rock on! Thanks for the link!

On a recent project, I had the need to copy one node to another 'parent' node. I just used duplicate() on the node and it worked fine.

I was told by a co-worker that it would not work because every XML node has a 'parentNode'. Apparently in CFMX 7, Cf is smart enough to remove that reference when you duplicate(). I am not certain how this would work if I tried to move it to a completely different XML document.

Ben,

Check out this XMLMerge UDF I created back in February which uses XSLT to merge.

http://www.intersuite.com/client/index.cfm/2007/2/15/XMLMerge-UDF-Uses-XSLT-to-merge-root-child-nodes

Regards,

Chris

@Chris,

That looks pretty cool. I know nothing about XSLT (I have tried to learn it but I just can't seem to get a handle on its seemly irregular programming syntax). I like what you are doing; my only issue with it is that you have to re-parse XML, which might have a lot of over head.

Cool stuff though. I really should learn more about XSLT.

Working with XML in Coldfusion is painful and slow. There are much better Java library options available. My blog entry details the problems and a solution using XOM and a StAX processor:

http://orangepips.instantspot.com/blog/index.cfm/2007/3/28/XML-StAX-Processing-with-Coldfusion

@Matt,

That is some interesting stuff. I have not done anything with XML outside of the core ColdFusion installed libraries. I will have to take a look at that other stuff sometime.

Just wanted to say thanks for writing this comment! I ran into this same issue while doing some XML work today, and this saved me a TON of headache. Thanks!

Hey ben this is great and it almost solved my problem. Im trying to import a specific child to another xml document in the same parent. I tried to tweak your function to accept a new argument for a specific child but it doesnt seem to be working. Some of these functions are new to me.

Thanks, this worked great for me.

This worked great for manipulating a Word 2003 XML document. I'm using it to insert the contents of one document into another.

So this will work with merging a bunch of xml documents that are identical in structure?

@Don,

You should be able to do that. It's an interesting problem.

Yup. Basically I have information coming in from many different sources. It is the same format so it would be nice to have an easy way to just merge the documents. Right now I have to parse each one and build a master. Many steps and very slow since they can have up to a million + entries between them all. (Sales information).

Twould be nice to just say XMLMerge(doc1,doc2) or something like that.

@Don,

I've been thinking about this issue and the one thing that I realize will happen is that ColdFusion won't have the ability to hold such a large XML file in memory. Why are you trying to merge them? For transfer?

Hi Ben,
just out of curiosity, why didn't you do the code to also copy the attributes of NodeA to NodeB if Any? Is there a specific reason? I did the code, I'm just wondering if there is anything I should know.

Thanks
Faisal

How about this one -
If you work with the Amazon API for products, you know that the nodes come out basically in reverse order for any item. It will give you the node for the product, then the parent, then for the parent it gives the grandparent and so on. All digging deeper into the xml.
<node>
<ancestor>
<node>
<ancsetor>
.... up to top level node
</ancestor>
</node>
</ancestor>
</node>
So how to flip it around so I have an xml doc with the top level node (category) on down?
Lots of work. That's how. sigh.
Actually I'm thinking of converting it to an array and then going from there. Or a structure.

@Faisal,

I believe the node import bring the attributes along with it.

@Don,

Hmmm, sounds funky. I assume they are returning it that way for a practical reason?? I don't have much experience with Amazon's web services (just played around with it once or twice).

Hi, I would like to know if this is possible?

If yoou have:

<cfxml variable="xmlDate">

<date>

<meal>
<location>Ben's Pizza</location>
<time>7:30 PM</time>
</meal>

<movie>
<name>Friends With Money</name>
<time>9:15 PM</time>
</movie>

</date>

</cfxml>

And:

<cfxml variable="xmlGirls">

<girls>
<girl id="1">
<name>Kit Cat</name>
<hair>Brunette</hair>
<eyes>Blue</eyes>
</girl>
<girl id="4">
<name>Anna Banana</name>
<hair>Brunette</hair>
<eyes>Brown</eyes>
</girl>
<girl id="5">
<name>Marcie Darcey</name>
<hair>Blonde</hair>
<eyes>Brown</eyes>
</girl>
</girls>

</cfxml>

And you want to add girls as children of the root element date...
Thanks :)

@Christophe,

The code I have above is for copy one node's children to the child nodes of another node (in another document). Since you want to add the ROOT element of one XML document to the children of another node (in another document), you'd have to update the code to work with that.

I think it would work in basically the same way - you'd have to access the underlying Java methods on the root node to change it's document owner.

Okay, 2 answers long time coming.
1 - The reason to merge the documents is for reporting purposes. The full document would only be created once each day at night. The server it is done on has 12G of ram so that is not a problem. (Dual quad core wooo hooo). I finally just said to myself "self, just chop off the top level opening and closing of each document, put them together, and then put the opening and closing back on." Works well.
2 - Why does Amazon do what it does? Who knows. lol I have found many of these big companies are trying to create their own way of doing APIs etc forcing us developers to jump through hoops. I think it may be like IE marching to the beat of a different drum but being big enough to force others to follow along.
Google is doing this too in their new Analytics API. What a nightmare they have there. It is like "Geeks Gone Wild". They were told "Come up with something that will confuse the snot out of the average developer just to show how smart you are"

arg

@Don,

Ha ha, Geeks gone wild :) It sounds like you might want to explore some XML transform stuff if you need to get Amazon nodes in a different order (sorry, I sort of lost the conversation a bit).

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