# XML - converting from one feed to another (beginner) **URL:** \ **Category:** Ruby\ **Created:** [December 29, 2006, 4:36pm UTC](https://www.ruby-forum.com/t/xml-converting-from-one-feed-to-another-beginner/80644 "2006-12-29T16:36:30Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [December 29, 2006, 4:36pm UTC](https://www.ruby-forum.com/t/xml-converting-from-one-feed-to-another-beginner/80644/1 "2006-12-29T16:36:30Z")
I’m trying to read an XML feed of products and convert them to a different XML feed to upload to Froogle (Google Base). How do I read the lines of XML and then rewrite them in the new XML? I’ve started with rexml, but I’m not sure if I’m on the right track. def convert\_to\_base\_xml(xml) # Takes a product XML feed and converts it into one that # is formatted for uploading to Google Base # doc = REXML::Document.new feed = REXML::Document.new(xml) # Create the export XML document doc = REXML:Document.new rss = doc.add\_element ‘rss’ channel = doc.add\_element ‘channel’ # Loop through old feed and create new feed based # on that data feed.each\_child do |child| #add items to new rss feed, see below ``` # I'm not sure what I should do here ``` end # Save rss feed to a file end # original feed XML # # # # \\ # # \\ # # \\ # # # # # # # # Convert to an RSS 2.0 feed in this format: # # # # # \\ # # \\ # \\ # \\ # \\ # \\ # ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [December 29, 2006, 6:43pm UTC](https://www.ruby-forum.com/t/xml-converting-from-one-feed-to-another-beginner/80644/2 "2006-12-29T18:43:02Z")
rb wrote: > # doc = REXML::Document.new > > feed = REXML::Document.new(xml) > > # Create the export XML document > > doc = REXML:Document.new You may be better off building the new XML using either direct string concatenating, or a lib such as Jim W.'s Builder (which will help ensure the result is proper XML). Or one of the Ruby RSS libraries. (I’d go with populating templates and just make sure the new content is correctly escaped.) The general ides is to loop over the item elements in the source DOM (using either REXML or Hpricot), extract the relevant data, and populate a new item element in the target XML. If you have a template for the target item element you can stuff in the new content on each pass of the loop and append it to the resulting XML. For example, with Hpricot (which you can install as a gem): require ‘hpricot’ … src\_dom = Hpricot(source\_rss\_xml). src\_dom/‘//item’.each do |el| title = (item/‘title’).text title\_url = (item/‘title\_url’).text # … # Now build the new item element for the target XML # and add it to the accumulating content end (For REXML it’s basically the same, but the XPath invocation is different.) Some considerations may be time and memory needs; if you are dealing with large documents, a pull or stream parser would be better, but it can be a bit harder to work with if you are new to it. But see my article in Dr. Dobbs: [http://www.ddj.com/184406385](http://www.ddj.com/184406385) Try the simplest approach first and see if it works, and if works well enough. – James B. [http://www.rubyaz.org](http://www.rubyaz.org) - Hacking in the Desert [http://www.jamesbritt.com](http://www.jamesbritt.com) - Playing with Better Toys ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [December 29, 2006, 8:01pm UTC](https://www.ruby-forum.com/t/xml-converting-from-one-feed-to-another-beginner/80644/3 "2006-12-29T20:01:26Z")
On Sat, 30 Dec 2006 02:40:18 +0900, James B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > (For REXML it’s basically the same, but the XPath invocation is different.) > > Some considerations may be time and memory needs; if you are dealing > with large documents, a pull or stream parser would be better, but it > can be a bit harder to work with if you are new to it. But see my > article in Dr. Dobbs: [http://www.ddj.com/184406385](http://www.ddj.com/184406385) > > Try the simplest approach first and see if it works, and if works well > enough. Thanks for those tips. I’m going to study what you wrote and see if I can make it work. The XML file is about 2.5 Mb, and the computers running the script have 1gb of RAM. ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [December 29, 2006, 8:15pm UTC](https://www.ruby-forum.com/t/xml-converting-from-one-feed-to-another-beginner/80644/4 "2006-12-29T20:15:26Z")
Hi rb, rb wrote: > I’m trying to read an XML feed of products and convert them to a > different XML feed to upload to Froogle (Google Base). > > How do I read the lines of XML and then rewrite them in the new XML? > I’ve started with rexml, but I’m not sure if I’m on the right track. Depending on whether or not you want to make further use of the content of your XML feed within your Ruby / Rails app (i.e., you actually _want_ the info stored in a database) you might be better off just doing the transform using XSLT. Best regards, Bill ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [December 29, 2006, 8:51pm UTC](https://www.ruby-forum.com/t/xml-converting-from-one-feed-to-another-beginner/80644/5 "2006-12-29T20:51:38Z")
On 29 Dec 2006 11:12:41 -0800, “bill walton” [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > of your XML feed within your Ruby / Rails app (i.e., you actually > _want_ the info stored in a database) you might be better off just > doing the transform using XSLT. Thanks… I didn’t think of that. I will have to learn XSLT. For now, I have to finish this XML for Google Base by tomorrow so I’m going to try to finish it with Ruby. Might try XSLT next. ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [January 1, 2007, 7:05pm UTC](https://www.ruby-forum.com/t/xml-converting-from-one-feed-to-another-beginner/80644/6 "2007-01-01T19:05:44Z")
On Sat, 30 Dec 2006 02:40:18 +0900, James B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > rb wrote: > > > I’m trying to read an XML feed of products and convert them to a > > different XML feed to upload to Froogle (Google Base). […] > # Now build the new item element for the target XML > > # and add it to the accumulating content > > end Thanks… it’s working so far, but I had to use this syntax: title = (el/‘title’).text ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [December 29, 2006, 10:37pm UTC](https://www.ruby-forum.com/t/xml-converting-from-one-feed-to-another-beginner/80644/7 "2006-12-29T22:37:57Z")
rb wrote: > Thanks… I didn’t think of that. I will have to learn XSLT. For > now, I have to finish this XML for Google Base by tomorrow so I’m > going to try to finish it with Ruby. Might try XSLT next. XSLT would be painful overkill for this sort of transformation. – James B. [http://www.ruby-doc.org](http://www.ruby-doc.org) - Ruby Help & Documentation [http://beginningruby.com](http://beginningruby.com) - Beginning Ruby: The Online Book [http://www.rubystuff.com](http://www.rubystuff.com) - The Ruby Store for Ruby Stuff [http://www.jamesbritt.com](http://www.jamesbritt.com) - Playing with Better Toys ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [January 1, 2007, 7:43pm UTC](https://www.ruby-forum.com/t/xml-converting-from-one-feed-to-another-beginner/80644/8 "2007-01-01T19:43:52Z")
> title = (el/‘title’).text Ah, good catch. Bug in my example code. – James B. “I have the uncomfortable feeling that others are making a religion out of it, as if the conceptual problems of programming could be solved by a single trick, by a simple form of coding discipline!” - Edsger Dijkstra ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [January 2, 2007, 12:51pm UTC](https://www.ruby-forum.com/t/xml-converting-from-one-feed-to-another-beginner/80644/9 "2007-01-02T12:51:23Z")
On 12/29/06, James B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > XSLT would be painful overkill for this sort of transformation. I’m going to have to disagree here - I’ve done a reasonable amount of XSLT work, and this is exactly the sort of thing it’s designed to do. In terms of effort and length of the resulting code, what you lose in verbose syntax (although it’s nowhere near as bad as some make out), you gain in not having to handle input/output/parsing/busy-work that would need to be done “manually” in Ruby.