win_xml module 'cannot call a method on a null-valued expression'

[Dave York]

I have an JBoss domain.xml file im trying to manipulate with win_xml:

<domain>
...
    <server-groups>
        <server-group name="sandbox" profile="full-ha">
            <jvm name="default">
                <heap size="8192m" max-size="8192m"/>
                <permgen max-size="384m"/>
            </jvm>
            <socket-binding-group ref="full-ha-sockets"/>
            <deployments>
                <deployment name="XXXXXXXXXXX.ear" runtime-name="XXXXXXXXXXX.ear"/>
            </deployments>
        </server-group>
    </server-groups>


</domain>

When I try to modify the heap size attribute above using win_xml with this play:

  - name: Test modifying XML

    win_xml:

      path: e:\jboss-eap-6.4\XXXXXXX\configuration\domain.xml

      xpath: '/domain/server-groups/server-group/jvm/heap'

      attribute: 'size'

      fragment: '123m'

      type: attribute

However, I get an exception that looks like its coming from powershell "You cannot call a method on a null-valued expression

"exception": "You cannot call a method on a null-valued expression.\r\nAt line:204 char:5\r\n+     [bool]$add = !$node.HasAttribute($attribute) -Or ($node.$attribut ...\r\n+     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\r\n    + CategoryInfo          : InvalidOperation: (:) [], ParentContainsErrorRecordException\r\n    + FullyQualifiedErrorId : InvokeMethodOnNull\r\n\r\nScriptStackTrace:\r\nat <ScriptBlock>, <No file>: line 204\r\n",

    "msg": "Unhandled exception while executing module: You cannot call a method on a null-valued expression.",
    "_ansible_no_log": false,
    "changed": false

}

Anyone see my problem? I checked the xpath using Notepad++ xml tools plugin and it seems correct.  Scratchin my head

[Dave York]

I forgot to add, the domain tag is:

<domain xmlns="urn:jboss:domain:1.8">

not just 

<domain>

if that's relevant.  

[Dave York]

I figured this out.  Turned out that my xml was using a different namespace? I had to follow guidance I found on stackoverflow:
https://stackoverflow.com/questions/5239685/xml-namespace-breaking-my-xpath

So my play now looks like this (and works):

  tasks:

  - name: Test modifying XML

    win_xml:

      path: e:\jboss-eap-6.4\XXXXXXXXX\configuration\domain.xml

      xpath: '/*[local-name()="domain"]/*[local-name()="server-groups"]/*[local-name()="server-group"]/*[local-name()="jvm"]/*[local-name()="heap"]'

[Dick Visser]

Hi

While that does work, it looks like the xpath expression is flattening too much with all those wildcards. 

The correct way would be to provide the actual namespace, this is supported by the module:

https://docs.ansible.com/ansible/latest/modules/xml_module.html#parameter-namespaces

Dick

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[Dick Visser]

Forget what I said - I misread. The win_xml module doesn't have a 'namespaces' option.

I mixed it up with the regular xml module.

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Dick Visser
Trust & Identity Service Operations Manager
GÉANT