Using some of your example, together with code i wrote to XMLify
simple python classes (like pickle, but xml out.input) I have got
something working that handles circular references and updates the
database after XML has been changed(e.g. in a client) and parsed
back.
It creates a reference dict with python function id(obj) as key
(registry[id(obj)] = obj) to later see whether an object has already
been written to or read from the XML string. This id is stored in the
XML tag (<TAGNAME ID = 1245125> something </TAGNAME>). If the id is
already in the registry, it will write new occurences of obj as
<TAGNAME ID = "1245125"/>. When the xml is read, basically the same
registry is created and used to look up objects that have been created
already.
I also stores the primary key(s) as XML attribute (<TAGNAME PK =
"(2325525,)"> something </TAGNAME>) to be able to look up the correct
database entry to be updated when the XML is read back
(session.query(cls).get(eval(element.get("PK")))..
The result looks something like this:
<somemodule.Address PK = "(1,)" ID = "46720168">
<int name = "id"> 1 </int>
<unicode name = "data"> bla bla </unicode>
<sqlalchemy.orm.collections.InstrumentedList name = "persons" ID =
"46689160">
<somemodule.Engineer PK = "(1,)" ID = "46695480">
<somemodule.Address PK = "(1,)" name = "address" ID =
"46720168"/>
<int name = "id"> 1 </int>
<int name = "address_id"> 1 </int>
<unicode name = "firstname"> john </unicode>
</somemodule.Engineer>
</sqlalchemy.orm.collections.InstrumentedList>
</somemodule.Address>
(xml attribute "name" is the name of the attribute)
If there is any interest i will post a sqlalchemy specific version of
the code, when it is somewhat ready.
Cheers, Lars
On Mar 26, 10:16 am, Julien Cigar <[email protected]> wrote:
> On 03/23/2012 10:37, lars van gemerden wrote:
>
> > Hi Julian,
>
> > Thanks, I am looking into it and it looks interesting. Have you done
> > much testing yet? How do you (plan to; haven't looked at too much
> > detail yet) check for circular references (like backrefs)?
>
> circular references aren't handled yet .. at the moment all what you can
> do is something like:
>
> >>> a = Page.query.get(454)
>
> >>> SAMappedSerializer(a).json(exclude_columns=('body', ),
> include_relations=('type', 'tags'))
> '{"updated": "2012-03-21T16:52:43Z", "added": "2009-10-16T14:23:24Z",
> "description": "The Belgian Biodiversity Platform", "effective": null,
> "tags": [{"description": null, "id": 26, "name": "Belspo"},
> {"description": null, "id": 29, "name": "Belgian Biodiversity
> Platform"}], "icon_content_id": null, "count_children": 0, "customized":
> false, "weight": 23, "owner_id": 1, "content_id": 454, "expiration":
> null, "polymorphic_loading": null, "state_id": 3, "title": "About us",
> "exclude_nav": false, "type": {"description": null, "icon": "page.png",
> "id": 2, "name": "page"}, "id": 454, "container_id": 1,
> "content_type_id": 2}'
>
> >>> SAMappedSerializer(a).xml(exclude_columns=('body', ),
> include_relations=('type', 'tags'))
> <content><updated>2012-03-21T16:52:43Z</updated><added>2009-10-16T14:23:24Z
> </added><description>The
> Belgian Biodiversity Platform</description><effective
> /><tags><tags_0><description
> /><id>26</id><name>Belspo</name></tags_0><tags_1><description
> /><id>29</id><name>Belgian Biodiversity
> Platform</name></tags_1></tags><icon_content_id
> /><count_children>0</count_children><customized>False</customized><weight>2
> 3</weight><owner_id>1</owner_id><content_id>454</content_id><expiration
> /><polymorphic_loading /><state_id>3</state_id><title>About
> us</title><exclude_nav>False</exclude_nav><type><description
> /><icon>page.png</icon><id>2</id><name>page</name></type><id>454</id><conta
> iner_id>1</container_id><content_type_id>2</content_type_id></content>
>
> etc
>
>
>
>
>
>
>
>
>
> > Cheers, Lars
>
> > On Thursday, March 22, 2012 11:36:41 AM UTC+1, lars van gemerden wrote:
>
> > Hi,
>
> > I am looking for a way to convert SQLalchemy objects to XML and
> > back, in order to support a webapplication. I made a mixin class
> > that does a decent job on 'normal' python objects (basically works
> > for in the same cases as pickle, though more testing is required).
> > I would prefer to have a simple mixin interface with something like:
>
> > def toXML():
> > 'convert attributes to xml'
> > return xmlstring
>
> > def fromXML(xmlstring)
> > 'update attributes from xml'
>
> > The most simple case would be that the web user request indicates
> > the primary key of the object, gets the corrsponding xml string in
> > return, changes fields in the xml string and posts it back, which
> > leads to an update of the object.
>
> > I have formulated a couple of initial questions:
>
> > - what attributes should be converted to and from xml?
> > - how do i handle foreign keys on the 'other' side?
>
> > Note that the object remains in memory during the user
> > interaction, so it does not have to be reinitialized from scratch.
>
> > Cheers, Lars
>
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