Re: Safely injecting VALUES into a SPARQL query

[Andy Seaborne]

On 25/11/2024 11:14, Martynas Jusevičius wrote:

Thanks Andy.

I cannot directly use QueryExecution because I'm executing remotely
using my own HTTP client (Jersey client).

But I suppose I can do to the query string what ExecHTTPBuilder is
doing to it? Is it as simple as

   queryActual = QueryTransformOps.transform(queryActual, substitutionMap);

? I'm looking here:
https://github.com/apache/jena/blob/main/jena-arq/src/main/java/org/apache/jena/http/sys/ExecHTTPBuilder.java#L331C13-L331C85

Yes.

On Mon, Nov 25, 2024 at 12:03 PM Andy Seaborne <a...@apache.org> wrote:

Another way is at execution time:

QueryExecution....
     .query(query string or object)
     .substitution(varName, value);

which uses QueryTransformOps.

      Andy


On 25/11/2024 08:40, Martynas Jusevičius wrote:

Hi Lorenz,

thanks, but wouldn't these methods append VALUES at the end of the
query? Which would not be equivalent to having it injected at the
beginning?

I don't want to build the whole query with Java -- I already have a
query string.

Martynas

On Mon, Nov 25, 2024 at 7:58 AM Lorenz Buehmann
<buehm...@informatik.uni-leipzig.de> wrote:

Hi,

you mentioned a query builder, so did you try to use the Jena query
builder already? If so,

the method addWhereValueVars on the SelectBuilder[1] or directly on the
WhereBuilder[2] would be the way to go.


Cheers,

Lorenz

[1]
https://jena.apache.org/documentation/javadoc/extras/querybuilder/org.apache.jena.querybuilder/org/apache/jena/arq/querybuilder/SelectBuilder.html#addWhereValueVars(java.util.Map)


[2]
https://jena.apache.org/documentation/javadoc/extras/querybuilder/org.apache.jena.querybuilder/org/apache/jena/arq/querybuilder/WhereBuilder.html#addWhereValueVars(java.util.Map)


On 25.11.24 01:02, David Habgood wrote:

Hi Martynas,

Do you know ahead of time which variable(s) you're going to be injecting
the VALUES clause for?

I've been using a pattern where I add VALUES ?this { UNDEF } in "template"
queries, then at runtime parse the query and replace "UNDEF" (where all of
the DataBlockValue <https://www.w3.org/TR/sparql11-query/#rDataBlockValue>s
in a binding within a InlineDataFull are "UNDEF") with a set of bindings
supplied at runtime. This has the benefit that if you do not supply a
binding for ?this, UNDEF means it is left unbound.

Thanks,

On Mon, Nov 25, 2024 at 9:40 AM Martynas Jusevičius <marty...@atomgraph.com>
wrote:

Hi,

What would be the simplest way to safely (i.e. using query builder or
algebra) to inject a VALUES block at the beginning of a query?

For example

SELECT *
{
     ?this ?p ?o
}

should become

SELECT *
{
     VALUES ?this <http://localhost>
     ?this ?p ?o
}

after the injection.

Thanks,

Martynas

--
Lorenz Bühmann
Research Associate/Scientific Developer

Email buehm...@infai.org

Institute for Applied Informatics e.V. (InfAI) | Goerdelerring 9 | 04109 
Leipzig | Germany