Using Python to comment out XML

Question

I'm trying (and failing) to comment out the HornetQ configuration from a JBoss 6.2 domain.xml file, instead of inserting a comment around the stanza I want to remove, I'm managing to delete everything remaining in the file.

The code I have so far is

from xml.dom import minidom
import os, time, shutil

domConf=('/home/test/JBoss/jboss-eap-6.2/domain/configuration/domain.xml')
commentSub=('urn:jboss:domain:messaging:1.4')


now=str(int(time.time())) 
bkup=(domConf+now)
shutil.copy2(domConf, bkup)

xmldoc = minidom.parse(domConf)
itemlist = xmldoc.getElementsByTagName('subsystem')
for s in itemlist:
        if commentSub in s.attributes['xmlns'].value:
            s.parentNode.insertBefore(xmldoc.createComment(s.toxml()), s)
file = open(domConf, "wb")
xmldoc.writexml(file)
file.write('\n')
file.close()

the configuration I'm trying to comment out is -

        <subsystem xmlns="urn:jboss:domain:messaging:1.4">
            <hornetq-server>
                <persistence-enabled>true</persistence-enabled>
                <journal-type>NIO</journal-type>
                <journal-min-files>2</journal-min-files>
                <connectors>
[....]
                    </pooled-connection-factory>
                </jms-connection-factories>
            </hornetq-server>
        </subsystem>

Thanks!

Answer 1

The problem you were running into was that the sections you are trying to comment out already contain XML comments. Nested comments are not allowed in XML. (See Nested comments in XML? for more info.)

I think what you need to do is this:

from xml.dom import minidom
import os, time, shutil

domConf=('/home/test/JBoss/jboss-eap-6.2/domain/configuration/domain.xml')
resultFile='result.xml'
commentSub=('urn:jboss:domain:messaging:1.4')

now=str(int(time.time()))
bkup=(domConf+now)
shutil.copy2(domConf, bkup)

xmldoc = minidom.parse(domConf)
itemlist = xmldoc.getElementsByTagName('subsystem')
for s in itemlist:
        if commentSub in s.attributes['xmlns'].value:
            commentText = s.toxml()
            commentText = commentText.replace('--', '- -')
            s.parentNode.insertBefore(xmldoc.createComment(commentText), s)
            s.parentNode.removeChild(s)
file = open("result.xml", "wb")
xmldoc.writexml(file)
file.write('\n')
file.close()

shutil.copy2(resultFile, domConf)

This finds the comment as you do, but before inserting it, changes any nested XML comments so they are no longer comments by replacing '--' with '- -'. (Note this will probably break the XML file structure if you uncomment that section. You'll have to reverse the process if you want it to parse again.) After inserting, the script deletes the original node. Then it writes everything to a temporary file, and uses shutil to copy it back over the original.

I tested this on my system, using the file you posted to the pastebin in the comment below, and it works.

Note that it's kind of a quick and dirty hack - because the script will also replace '--' with '- -' everywhere in that section, and if there is other text as part of an XML node that has '--' in it, it too will get replaced...

The right way to do this would probably be to use lxml's elementtree implementation, use lxml's XSL to select only comments within the section, and either delete or transform them appropriately - so you don't mess up non-commented text. But that's probably beyond the scope of what you asked. (Python's built-in elementtree doesn't have a complete XSL implementation and probably can't be used to select comments.)