我想用arq jena写一个属性函数扩展sparql,怎么写?要求:
SELECT *
WHERE {?Person f:Next(name) ?x.}
我的功能代码:
import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.apache.jena.atlas.logging.Log;
import org.apache.jena.graph.Node;
import org.apache.jena.query.QueryBuildException;
import org.apache.jena.query.QueryException;
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.engine.ExecutionContext;
import org.apache.jena.sparql.engine.QueryIterator;
import org.apache.jena.sparql.engine.binding.Binding;
import org.apache.jena.sparql.engine.iterator.QueryIterNullIterator;
import org.apache.jena.sparql.pfunction.PFuncSimple;
import org.apache.jena.sparql.pfunction.PFuncSimpleAndList;
import org.apache.jena.sparql.pfunction.PropFuncArg;
import org.apache.jena.sparql.pfunction.PropertyFunction;
import org.apache.jena.sparql.pfunction.PropertyFunctionFactory;
import org.apache.jena.sparql.util.IterLib;
public class Next implements PropertyFunctionFactory {
@Override
public PropertyFunction create(final String uri)
{
return new PFuncSimple()
{
@Override
public QueryIterator execEvaluated(final Binding parent, final Node subject, final Node predicate, final Node object, final ExecutionContext execCxt)
{
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();
从 rdf 中提取 sebject 、 predicate 和 object :
for (;iter.hasNext();) {
Statement stmt = iter.nextStatement();
Resource sub = stmt.getSubject();
Property pred = stmt.getPredicate();
RDFNode obj = stmt.getObject();
将 rdf 的主语和谓词与请求的主语和谓词进行比较
if ((sub.toString().equals(subject.toString()))|| (pred.toString().equals(predicate.toString())))
return new QueryIterPlainWrapper ((Iterator<Binding>) obj,execCxt);
}
return null;
}
};
}
}
以及如何注册我的功能