lxml and xpath(?)
Doug OLeary
dkoleary at olearycomputers.com
Mon Oct 24 17:41:05 EDT 2016
Hey;
Reasonably new to python and incredibly new to xml much less trying to parse it. I need to identify cluster nodes from a series of weblogic xml configuration files. I've figured out how to get 75% of them; now, I'm going after the edge case and I'm unsure how to proceed.
Weblogic xml config files start with namespace definitions then a number of child elements some of which have children of their own.
The element that I'm interested in is <server> which will usually have a subelement called <listen-address> containing the hostname that I'm looking for.
Following the paradigm of "we love standards, we got lots of them", this model doesn't work everywhere. Where it doesn't work, I need to look for a subelement of <server> called <machine>. That element contains an alias which is expanded in a different root child, at the same level as <server>.
So, picture worth a 1000 words:
<?xml version='1.0' encoding='UTF-8'?>
< [[ heinous namespace xml snipped ]] >
<name>[[text]]</name>
...
<server>
<name>EDIServices_MS1</name>
...
<machine>EDIServices_MC1</machine>
...
</server>
<server>
<name>EDIServices_MS2</name>
...
<machine>EDIServices_MC2</machine>
...
</server>
<machine xsi:type="unix-machineType">
<name>EDIServices_MC1</name>
<node-manager>
<name>EDIServices_MC1</name>
<nm-type>SSL</nm-type>
<listen-address>host001</listen-address>
<listen-port>7001</listen-port>
</node-manager>
</machine>
<machine xsi:type="unix-machineType">
<name>EDIServices_MC2</name>
<node-manager>
<name>EDIServices_MC2</name>
<listen-address>host002</listen-address>
<listen-port>7001</listen-port>
</node-manager>
</machine>
</domain>
So, running it on 'normal' config, I get:
$ ./lxml configs/EntsvcSoa_Domain_config.xml
EntsvcSoa_CS => host003.myco.com
EntsvcSoa_CS => host004.myco.com
Running it against the abi-normal config, I'm currently getting:
$ ./lxml configs/EDIServices_Domain_config.xml
EDIServices_CS => EDIServices_MC1
EDIServices_CS => EDIServices_MC2
Using the examples above, I would like to translate EDIServices_MC1 and EDIServices_MC2 to host001 and host002 respectively.
The primary loop is:
for server in root.findall('ns:server', namespaces):
cs = server.find('ns:cluster', namespaces)
if cs is None:
continue
# cluster_name = server.find('ns:cluster', namespaces).text
cluster_name = cs.text
listen_address = server.find('ns:listen-address', namespaces)
server_name = listen_address.text
if server_name is None:
machine = server.find('ns:machine', namespaces)
if machine is None:
continue
else:
server_name = machine.text
print("%-15s => %s" % (cluster_name, server_name))
(it's taken me days to write 12 lines of code... good thing I don't do this for a living :) )
Rephrased, I need to find the <listen-address> under the <machine> child who's name matches the name under the corresponding <server> child. From some of the examples on the web, I believe xpath might help but I've not been able to get even the simple examples working. Go figure, I just figured out what a namespace is...
Any hints/tips/suggestions greatly appreciated especially with complete noob tutorials for xpath.
Thanks for your time.
Doug O'Leary
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