/**
* Returns a collection of RDFStatements that match the described subject
*
* @param subject Subject
* @return collection of RDFStatements
*/
public Collection<RDFStatement> getStatements(String subject) {
if (subject == null || subject.isEmpty()) {
return null;
}
List<RDFStatement> statement = null;
try {
// define a describe query
String query = String.format("DESCRIBE %s FROM < %s >", subject, this.graphName);
logger.debug("Query: \n{}", query);
Query sparqlQuery = QueryFactory.create(query);
VirtuosoQueryExecution vqe = VirtuosoQueryExecutionFactory.create(sparqlQuery, this.graph);
// execute the query and get the graph
Model model = vqe.execDescribe();
Graph queriedGraph = model.getGraph();
// itreate over the retrieved triples, and place them inside a list
ExtendedIterator<Triple> iter = queriedGraph.find(Node.ANY, Node.ANY, Node.ANY);
statement = new ArrayList<>();
while (iter.hasNext()) {
Triple t = (Triple) iter.next();
RDFStatement stmt =
new RDFStatement(
t.getSubject().toString(), t.getPredicate().toString(), t.getObject().toString());
statement.add(stmt);
}
} catch (Exception ex) {
logger.error("Exception occured while querying for statements", ex);
}
return statement;
}
public ResultSet executeQuery(String query, VirtDataset virtDataset) {
VirtGraph vg =
new VirtGraph(
virtDataset.getGraphUrl(), virtDataset.getGraphUser(), virtDataset.getGraphPassword());
VirtuosoQueryExecution vur = VirtuosoQueryExecutionFactory.create(query, vg);
ResultSet rs = vur.execSelect();
return rs;
}
/**
* Selects a triple by providing an RDFStatement object collection
*
* @param stmts
* @return Query result
*/
public List<RDFStatement> selectTriples(Collection<? extends RDFStatement> stmts) {
if (stmts == null || stmts.isEmpty()) {
return null;
}
RDFStatement rdfs = stmts.stream().findFirst().get();
String si = rdfs.getSubject(),
pi = rdfs.getPredicate(),
oi = rdfs.getObject(); // doesnt get value
StringBuilder sb = new StringBuilder();
stmts
.stream()
.forEach(
s -> {
s.setObject(RDFUtils.escapeString(s.getObject()));
sb.append(s.getSubject())
.append(" ")
.append(s.getPredicate())
.append(" ")
.append(s.getObject())
.append(" .\n");
});
String query =
String.format(
this.defaultPrefices + "SELECT * FROM <%s> WHERE { %s }",
this.graphName,
sb.toString());
Query sparqlQuery = QueryFactory.create(query);
VirtuosoQueryExecution vqe = VirtuosoQueryExecutionFactory.create(sparqlQuery, this.graph);
List<RDFStatement> stmtsList = new ArrayList<>();
ResultSet rs = vqe.execSelect();
while (rs.hasNext()) {
QuerySolution qs = rs.nextSolution();
RDFNode s = qs.get(si);
RDFNode p = qs.get(pi);
RDFNode o = qs.get(oi);
RDFStatement stmt =
new RDFStatement(
s != null ? s.toString() : "null",
p != null ? p.toString() : "null",
o != null ? RDFUtils.escapeString(o.toString()) : "null");
stmtsList.add(stmt);
logger.info("fetched: {}", stmt.toString());
}
return stmtsList;
}
