rdf jena api compared subject predicate object - api

Question

I created a function of extension sparql! how I can compare the subject,object and proopriété of rdf file with the parameter of the function which are (subject, property, object)?
This is my function but it does not display any result!
import static com.sun.org.apache.xalan.internal.xsltc.compiler.util.Type.String;
import java.*;
import java.io.*;**strong text**
import java.util.HashMap;
import java.util.Map;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.apache.jena.datatypes.xsd.XSDDatatype;
import org.apache.jena.rdf.model.Model;
import org.apache.jena.rdf.model.ModelFactory;
import org.apache.jena.rdf.model.Property;
import org.apache.jena.rdf.model.RDFNode;
import org.apache.jena.rdf.model.Resource;
import org.apache.jena.rdf.model.Statement;
import org.apache.jena.rdf.model.StmtIterator;
import org.apache.jena.sparql.expr.NodeValue;
import org.apache.jena.sparql.function.Function;
import org.apache.jena.sparql.function.FunctionBase2;
import org.apache.jena.sparql.function.FunctionFactory;
import static org.apache.jena.vocabulary.RDF.Nodes.object;
import static org.apache.jena.vocabulary.RDF.Nodes.predicate;
import static org.apache.jena.vocabulary.RDF.Nodes.subject;
public class haschild extends FunctionBase2 implements FunctionFactory{
private Map _cache;
public haschild()
{
_cache = new HashMap();
}
#Override
public NodeValue exec(NodeValue v1, NodeValue v2) {
String value = v2.asString();
String value2 = v1.asString();
Model model = ModelFactory.createDefaultModel();
InputStream is = null;
try {
is = new BufferedInputStream(
new FileInputStream( "C:\\\\fichier rdf/journal.webscience.org-vivo.rdf"));
} catch (FileNotFoundException ex) {
Logger.getLogger(haschild.class.getName()).log(Level.SEVERE, null, ex);
}
model.read(new InputStreamReader(is), "");
StmtIterator iter = model.listStatements();
// affiche l'objet, le prédicat et le sujet de chaque déclaration
while (iter.hasNext()) {
Statement stmt = iter.nextStatement(); // obtenir la prochaine déclaration
Resource subject = stmt.getSubject(); // obtenir le sujet
Property predicate = stmt.getPredicate(); // obtenir le prédicat
RDFNode object = stmt.getObject(); // obtenir l'objet
if((value2.equals(subject.toString()))&&(object.toString().equals(value))&&(predicate.toString().equals("http://www.w3.org/2000/01/rdf-schema#HasChild")))
return NodeValue.TRUE;
return NodeValue.FALSE;}
return null;
}
#Override
public Function create(String uri) {
throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.}
}

Answer 1

Compare the Nodes that back the various items and .equals those.
See NodeValue#asNode and RDFNode.asNode.
If you want value-equality (e.g. 1 equals +1.0e0), convert the RDFNode.asNode to a NodeValue and use NodeValue.sameAs.
NodeValue.asString returns the SPARQL syntax version of the value. Not for use in comparisons.