[Engine-devel] Issue with XML namespaces in engine-setup

[Daniel Veillard]

On Tue, Apr 10, 2012 at 01:54:51PM +0200, Juan Hernandez wrote:
> Hello,
> 
> The code that we use in engine-setup to modify JBoss AS XML
> configuration files uses the following pattern:
> 
> datasourceStr = '''
>     <datasource ...>
>        ...
>     </datasource>
> '''
> 
> xmlObj.addNodes("//datasource:subsystem/datasource:datasources",
> datasourceStr)
> 
> This looks correct but is in fact generating a incorrect XML document,
> as the tags being added are not associated to a namespace. The resulting
> XML file will be correct, but the temporary representation in memory is
> not. This causes problems if you later, before writing out the modified
> file, try to use xpath expressions matching the added nodes: there will
> be no match.
> 
> I would suggest that we change the pattern to something like this:
> 
> datasourceStr = '''
>   <any_dummy_tag xmlns="urn:jboss:domain:datasources:1.0">
>     <datasource ...>
>        ...
>     </datasource>
>   </any_dummy_tag>
> '''
> datasourceNodes = libxml2.parseDoc(datasourceStr).getRootElement().children
> 
> xmlObje.addNodes("//datasource:subsystem/datasource:datasources",
> datasourceNodes)
> 
> This way both the representation in memory and the resulting file are
> correct.
> 
> Le me know what you think.

  I think it's dangerous to move nodes from one document to another
especially if there is namespaces (I assume you're operating in an
environment on top of libxml2 as I saw a reference to it ;-)

  For libxml2 there is an API in C:
    http://xmlsoft.org/html/libxml-parser.html#xmlParseInNodeContext
which could do what you expect. Maybe there is a binding/wrapper
available you could use.

Also your "//datasource:subsystem/datasource:datasources" XPath query
could lead to multiple result nodes, I would suggest to pick the first
result only, I suppose you don't want to add the set of nodes to
multiple places

  xmlObje.addNodes("(//datasource:subsystem/datasource:datasources)[1]",
                   datasourceNodes)

 or something equivalent (unless addNodes() takes care to handle that
 properly ...)

Daniel

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