On Thu, Aug 1, 2013 at 10:12 AM, Andy Seaborne <[email protected]> wrote:
> On 01/08/13 01:52, Holger Knublauch wrote:
>>
>> I am upgrading our code base to the latest Jena snapshot, and noticed
>> that UpdateProcessor.setInitialBindings is no longer around. What is the
>> replacement for this functionality?
>>
>> Thanks
>> Holger
>>
>
> Holger,
>
> https://jena.apache.org/documentation/query/parameterized-sparql-strings.html
> http://jena.apache.org/documentation/javadoc/arq/com/hp/hpl/jena/query/ParameterizedSparqlString.html
It's also possible to simulate the initial bindings by using a VALUES
block on the query. This also has the advantage that it can be used
for binding a number of solutions at once. Here's an example:
import java.io.ByteArrayInputStream;
import java.util.ArrayList;
import java.util.List;
import com.hp.hpl.jena.query.Query;
import com.hp.hpl.jena.query.QueryExecutionFactory;
import com.hp.hpl.jena.query.QueryFactory;
import com.hp.hpl.jena.query.QuerySolution;
import com.hp.hpl.jena.query.ResultSet;
import com.hp.hpl.jena.query.ResultSetFormatter;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.rdf.model.ModelFactory;
import com.hp.hpl.jena.rdf.model.RDFNode;
import com.hp.hpl.jena.sparql.core.Var;
import com.hp.hpl.jena.sparql.engine.binding.Binding;
import com.hp.hpl.jena.sparql.engine.binding.BindingFactory;
public class ValuesInsteadOfInitialBindings {
@SuppressWarnings("serial")
public static void main(String[] args) {
final String ttlContent = "" +
"@prefix : <http://example.org/> .\n" +
"\n" +
":a :p :x ;\n" +
" :q :aa .\n" +
":b :p :x ;\n" +
" :q :bb .\n" +
":c :p :y.\n" +
"";
// Setup a model with the data above
final Model model = ModelFactory.createDefaultModel();
model.read( new ByteArrayInputStream( ttlContent.getBytes() ),
null, "TTL" );
final String thingsThatPX = ""+
"prefix : <http://example.org/>\n" +
"select * where {\n" +
" ?thing :p :x .\n" +
"}\n" +
"";
// Get a result set that binds ?thing to each value that :x
// as a value for :p
final ResultSet results = QueryExecutionFactory.create(
thingsThatPX, model ).execSelect();
// A query that retrieves the ?qValue of each ?thing. ?thing
here
has no binding
// and would match *everything* that has a value for :q.
final String qOfThings = "" +
"prefix : <http://example.org/>\n" +
"select * where {\n" +
" ?thing :q ?qValue .\n" +
"}\n" +
"";
// Create the query and show it, before setting up
// any VALUES.
final Query query = QueryFactory.create( qOfThings );
System.out.println( query );
// Create variables and bindings for the VALUES block
final List<Var> variables = new ArrayList<Var>() {{
for ( final String varName : results.getResultVars() ) {
add( Var.alloc( varName ));
}
}};
final List<Binding> bindings = new ArrayList<Binding>() {{
while ( results.hasNext() ) {
final QuerySolution solution = results.next();
for ( final Var var : variables ) {
add( BindingFactory.binding( var,
solution.get( var.getName()
).asNode() ));
}
}
}};
// Set the VALUES block and show the query again.
query.setValuesDataBlock( variables, bindings );
System.out.println( query );
// Show the final results
ResultSetFormatter.out( QueryExecutionFactory.create( query,
model
).execSelect() );
}
}
--
Joshua Taylor, http://www.cs.rpi.edu/~tayloj/
