/**
* Builds a String result for Elastic Search from an RDFNode
*
* @param node An RDFNode representing the value of a property for a given resource
* @return If the RDFNode has a Literal value, among Boolean, Byte, Double, Float, Integer Long,
* Short, this value is returned, converted to String
* <p>If the RDFNode has a String Literal value, this value will be returned, surrounded by
* double quotes
* <p>If the RDFNode has a Resource value (URI) and toDescribeURIs is set to true, the value
* of @getLabelForUri for the resource is returned, surrounded by double quotes. Otherwise,
* the URI will be returned
*/
private String getStringForResult(RDFNode node, boolean getNodeLabel) {
String result = "";
boolean quote = false;
if (node.isLiteral()) {
Object literalValue = node.asLiteral().getValue();
try {
Class<?> literalJavaClass = node.asLiteral().getDatatype().getJavaClass();
if (literalJavaClass.equals(Boolean.class)
|| Number.class.isAssignableFrom(literalJavaClass)) {
result += literalValue;
} else {
result = EEASettings.parseForJson(node.asLiteral().getLexicalForm());
quote = true;
}
} catch (java.lang.NullPointerException npe) {
result = EEASettings.parseForJson(node.asLiteral().getLexicalForm());
quote = true;
}
} else if (node.isResource()) {
result = node.asResource().getURI();
if (getNodeLabel) {
result = getLabelForUri(result);
}
quote = true;
}
if (quote) {
result = "\"" + result + "\"";
}
return result;
}
/**
* Returns the string value of the first of the properties in the uriDescriptionList for the given
* resource (as an URI). In case the resource does not have any of the properties mentioned, its
* URI is returned. The value is obtained by querying the endpoint and the endpoint is queried
* repeatedly until it gives a response (value or the lack of it)
*
* <p>It is highly recommended that the list contains properties like labels or titles, with test
* values.
*
* @param uri - the URI for which a label is required
* @return a String value, either a label for the parameter or its value if no label is obtained
* from the endpoint
*/
private String getLabelForUri(String uri) {
String result;
if (uriLabelCache.containsKey(uri)) {
return uriLabelCache.get(uri);
}
for (String prop : uriDescriptionList) {
String innerQuery = "SELECT ?r WHERE {<" + uri + "> <" + prop + "> ?r } LIMIT 1";
try {
Query query = QueryFactory.create(innerQuery);
QueryExecution qExec = QueryExecutionFactory.sparqlService(rdfEndpoint, query);
boolean keepTrying = true;
while (keepTrying) {
keepTrying = false;
try {
ResultSet results = qExec.execSelect();
if (results.hasNext()) {
QuerySolution sol = results.nextSolution();
result = EEASettings.parseForJson(sol.getLiteral("r").getLexicalForm());
if (!result.isEmpty()) {
uriLabelCache.put(uri, result);
return result;
}
}
} catch (Exception e) {
keepTrying = true;
logger.warn("Could not get label for uri {}. Retrying.", uri);
} finally {
qExec.close();
}
}
} catch (QueryParseException qpe) {
logger.error("Exception for query {}. The label cannot be obtained", innerQuery);
}
}
return uri;
}