/**
* Used to write Resources for a Subject. Literals will by-pass this method and use "Literal"
* method.
*
* @param predicate PredicateNode
* @param object ObjectNode
* @param writer PrintWriter
* @throws GraphException
*/
protected void writeStatement(
Graph graph,
SubjectNode subject,
PredicateNode predicate,
ObjectNode object,
PrintWriter writer)
throws GraphException {
// Literals are written differently
if (object instanceof Literal) {
this.writeStatement(graph, subject, predicate, (Literal) object, writer);
} else if (object instanceof BlankNode) {
// write as: <predicateURI> *blank node as subject* </predicateURI>
writer.println(" <" + this.getURI(predicate) + ">");
// write blank node as a "subject"
this.writeSubject(graph, (BlankNode) object, writer);
writer.println(" </" + this.getURI(predicate) + ">");
} else if (subject instanceof BlankNode) {
// predicatNode representing RDF Type
PredicateNode rdfTypeNode = null;
try {
rdfTypeNode = graph.getElementFactory().createResource(RDF.TYPE);
} catch (GraphElementFactoryException factoryException) {
throw new GraphException("Could not create RDF Type node.", factoryException);
}
// do not write the RDF Type element
if (!rdfTypeNode.equals(predicate)) {
// write as: <predicateURI rdf:resource="resourceURI"/>
writer.println(
" <"
+ this.getURI(predicate)
+ " "
+ RDF_PREFIX
+ ":resource=\""
+ this.getNodeString(object)
+ "\"/>");
}
} else {
// write as: <predicateURI rdf:resource="resourceURI"/>
writer.println(
" <"
+ this.getURI(predicate)
+ " "
+ RDF_PREFIX
+ ":resource=\""
+ this.getNodeString(object)
+ "\"/>");
}
}
/**
* Finds the RDF Type for a given subject.
*
* @param graph Graph
* @param subject SubjectNode
* @throws GraphException
* @return ObjectNode
*/
protected ObjectNode getSubjectType(Graph graph, SubjectNode subject) throws GraphException {
// value to be returned
ObjectNode type = null;
// validate graph
if ((graph == null)) {
throw new IllegalArgumentException("Graph argument must not be null.");
}
// predicatNode representing RDF Type
PredicateNode rdfType = null;
try {
rdfType = graph.getElementFactory().createResource(RDF.TYPE);
} catch (GraphElementFactoryException factoryException) {
throw new GraphException("Could not create RDF Type node.", factoryException);
}
// get the Subject's RDF type
ClosableIterator<Triple> typeIter = graph.find(subject, rdfType, null);
if (typeIter != null) {
// validate "first" triple and extract it's object (rdf type)
if (typeIter.hasNext()) {
Triple typeTriple = typeIter.next();
if (typeTriple != null) {
type = ((Triple) typeTriple).getObject();
} else {
throw new GraphException(
"Could not find RDF type for Subject: " + subject + " . Invalid Triple returned.");
}
}
// close the Iterator
typeIter.close();
}
return type;
}