Programmatically constructing sequences ("a", "b", "c") for XQuery

[George Feinberg]

On Aug 10, 2009, at 12:25 PM, Michael Ludwig wrote:

> Adam Retter schrieb:
>> I think the problem is that we are missing the bigger picture of the
>> XQuery.
>>
>> You have some XQuery and you want to construct a sequence of strings,
>> how in the XQuery do you get access to the data that you want to form
>> a sequence of strings from?
>
> Hi Adam,
>
> you're absolutely right - I forgot to include the context; sorry for
> that. The parameter is supplied programmatically in the query context,
> which holds prefix-namespace-mappings, variables, etc. (For more  
> detail,
> see XmlQueryContext in the DBXML documentation.)
>
> Using a literal:
>
>  xqc.setVariableValue("files", new XmlValue("eins"));
>
> Using a StringBuilder:
>
>  xqc.setVariableValue("files", new XmlValue(sb.toString()));
>
> Does that make it clear enough?
>
> I think I know what the problem is. The XmlValue constructor does not
> seem designed to accept sequences. What I mean to be a sequence -
> ('eins','zwei','drei') - is interpreted as a literal string.

You can set variable values that are sequences.  That is actually
the default.  The XmlValue-based version is just a short-cut
for the XmlResults-based variant.

Use:
XmlResults res = mgr.createResults();
res.addValue(new XmlValue(...));
res.addValue(new XmlValue(...));
res.addValue(new XmlValue(...));
xqc.setVariableValue("files", res);

George

>
> So I think a (somewhat kludgy) solution would be to construct a mini
> document from the input parameters, store it in the database and then
> join against that:
>
> <Params>
>  <F>eins</F>
>  <F>zwei</F>
>  <F>drei</F>
> </Params>
>
> Or, preferably, use an XmlResolver. Much better than storing  
> parameters
> in the database, if only temporarily.
>
> -- 
> Michael Ludwig
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