Question

下面是我简单的sparql查询。我想更改我的sparql查询uri，但我不知道如何在不使用输入/输出的情况下更改此特定内容。

输入字符串：

PREFIX ab: <http://learningsparql.com/ns/addressbook#> 

SELECT ?craigEmail
WHERE
{ ab:craig ab:email ?craigEmail . }

输出字符串：

PREFIX ab: <http://example.com#> 

SELECT ?craigEmail
WHERE
{ ab:craig ab:email ?craigEmail . }

请你在jena中为我提供这个简单的代码...

Answer 1

您可以使用Jena ARQ API并通过迭代SPARQL查询的三元模式元素以编程方式替换前缀ab的命名空间：

import org.apache.jena.graph.Node;
import org.apache.jena.graph.NodeFactory;
import org.apache.jena.graph.Triple;
import org.apache.jena.query.Query;
import org.apache.jena.query.QueryFactory;
import org.apache.jena.sparql.core.TriplePath;
import org.apache.jena.sparql.syntax.ElementPathBlock;
import org.apache.jena.sparql.syntax.ElementTriplesBlock;
import org.apache.jena.sparql.syntax.ElementVisitorBase;
import org.apache.jena.sparql.syntax.ElementWalker;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class Test {

public static void main(String[] args) {
        Query query = QueryFactory.create("" +
                "PREFIX ab: <http://learningsparql.com/ns/addressbook#> " +
                "SELECT ?craigEmail WHERE { ab:craig ab:email ?craigEmail . }");

        // This will walk through all parts of the query// This will walk through all parts of the query

        final String ns = "http://example.com#";

        ElementWalker.walk(query.getQueryPattern(), new ElementVisitorBase() { // ...when it's a block of triples...
            public void visit(ElementPathBlock el){ // ...go through all the triples...
                Iterator<TriplePath> triples = el.patternElts();
                List<Triple> newTriples = new ArrayList<>();
                while (triples.hasNext()) {
                    TriplePath triple = triples.next();
                    if(triple.isTriple()) {
                        Node s = triple.getSubject();
                        if(s.isURI()) {
                            String localName = s.getLocalName();
                            s = NodeFactory.createURI(ns + localName);
                        }
                        Node p = triple.getPredicate();
                        if(p.isURI()) {
                            String localName = p.getLocalName();
                            p = NodeFactory.createURI(ns + localName);
                        }
                        Node o = triple.getSubject();
                        if(o.isURI()) {
                            String localName = o.getLocalName();
                            o = NodeFactory.createURI(ns + localName);
                        }

                        newTriples.add(Triple.create(s, p, o));


                    } else {
                        // TODO handle triple path
                    }
                    triples.remove();
                }
                for(Triple t : newTriples) {
                    el.addTriple(t);
                }
            }

            @Override
            public void visit(ElementTriplesBlock el) {
                Iterator<Triple> triples = el.patternElts();
                List<Triple> newTriples = new ArrayList<>();
                while (triples.hasNext()) {
                    Triple triple = triples.next();

                    Node s = triple.getSubject();
                    if(s.isURI()) {
                        String localName = s.getLocalName();
                        s = NodeFactory.createURI(ns + localName);
                    }
                    Node p = triple.getPredicate();
                    if(p.isURI()) {
                        String localName = p.getLocalName();
                        p = NodeFactory.createURI(ns + localName);
                    }
                    Node o = triple.getSubject();
                    if(o.isURI()) {
                        String localName = o.getLocalName();
                        o = NodeFactory.createURI(ns + localName);
                    }

                    newTriples.add(Triple.create(s, p, o));

                    triples.remove();
                }
                for(Triple t : newTriples) {
                    el.addTriple(t);
                }
            }
        });

        query.setPrefix("ab", ns);
        System.out.println(query);
    }
}

改变uri而不使用jena中的输入输出

1 个答案: