/**
* 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;
}
/**
* Inserts a statement into the graph
*
* @param stmt Statement (RDFStatement triple)
* @return true if and only if the query execution was successful
*/
public boolean insertStatement(RDFStatement stmt) {
if (stmt == null) {
return false;
}
try {
stmt.setObject(RDFUtils.escapeString(stmt.getObject()));
String query = "INSERT INTO GRAPH <" + this.graphName + "> { " + stmt.toString() + "}";
VirtuosoUpdateRequest vur = VirtuosoUpdateFactory.create(query, this.graph);
vur.exec();
return true;
} catch (Exception ex) {
logger.error("Exception while inserting a statement", ex);
}
return false;
}
/**
* Delete a statement from a graph
*
* @param stmt (RDFStatement triple)
* @return true if and only if the query execution was successful
*/
public boolean deleteStatement(RDFStatement stmt) {
if (stmt == null) {
return false;
}
try {
stmt.setObject(RDFUtils.escapeString(stmt.getObject()));
String query =
String.format(
"DELETE FROM GRAPH <%s> { %s }",
this.graphName, RDFUtils.escapeString(stmt.toString()));
VirtuosoUpdateRequest vur = VirtuosoUpdateFactory.create(query, this.graph);
vur.exec();
return true;
} catch (Exception ex) {
logger.error("Exception while deleting a statement", ex);
}
return false;
}