private string ProcessNode(EntitySetQueryNode entitySet)
{
var entitySetType = _map.GetUriForType(entitySet.EntitySet.ElementType.FullName());
if (entitySetType == null)
{
// Throw exception
}
var instancesVariable = _sparqlModel.NextVariable();
_sparqlModel.RootGraphPattern.Add(
new TriplePattern(
new VariablePatternItem(instancesVariable),
new UriPatternItem("http://www.w3.org/1999/02/22-rdf-syntax-ns#type"),
new UriPatternItem(entitySetType)
));
_sparqlModel.AddSelectVariable(instancesVariable, entitySet.ItemType.FullName(), true);
_sparqlModel.IsDescribe = true;
return(instancesVariable);
}
/// <summary>
/// Creates an OData feed response containing a list of entries for a particular type of entity
/// </summary>
/// <param name="resultsGraph">The RDF graph containing the SPARQL results</param>
/// <param name="entityType">The fully qualified domain name for the type of entity to be written</param>
/// <param name="resultsCount">The count of the total number of results that the server can provide</param>
/// <param name="originalQueryModel">The SPARQL query that was executed to generate this graph</param>
public void CreateFeedFromGraph(IGraph resultsGraph, string entityType, int resultsCount, SparqlModel originalQueryModel = null)
{
var msgWriter = new ODataMessageWriter(_response, _writerSettings, _map.Model);
var feedWriter = msgWriter.CreateODataFeedWriter();
var entries = new List <ODataEntry>();
var typeUri = _map.GetUriForType(entityType);
if (!String.IsNullOrEmpty(typeUri))
{
var predNode = resultsGraph.CreateUriNode(UriFactory.Create(RdfConstants.RdfType));
var objNode = resultsGraph.CreateUriNode(UriFactory.Create(typeUri));
if (originalQueryModel == null || originalQueryModel.Ordering == null)
{
// No sorting required, just iterate all instances
foreach (var instanceTriple in resultsGraph.GetTriplesWithPredicateObject(predNode, objNode))
{
var instanceUri = (instanceTriple.Subject as IUriNode).Uri;
entries.Add(CreateODataEntry(resultsGraph, instanceUri.ToString(), entityType));
}
}
else
{
// We need to apply the same sort criteria to this graph to ensure
// that the ODATA results are properly sorted.
// NOTE: This will only work if all the properties used in the original query
// are present in the graph - this could be a problem with more complex traversals
// and the query may instead need to be rewritten / regenerated to extract only
// the required sort properties.
originalQueryModel.IsDescribe = false;
var resultsTable =
resultsGraph.ExecuteQuery(originalQueryModel.GetSparqlRepresentation()) as SparqlResultSet;
var targetVariable = originalQueryModel.SelectVariables[0];
foreach (var result in resultsTable.Results)
{
var instanceUriNode = result[targetVariable] as IUriNode;
if (instanceUriNode != null)
{
entries.Add(CreateODataEntry(resultsGraph, instanceUriNode.Uri.ToString(), entityType));
}
}
}
}
var feed = new ODataFeed {
Id = _baseUri + _map.GetTypeSet(entityType)
};
if (_writerSettings.Version >= ODataVersion.V2)
{
feed.Count = resultsCount;
}
if (originalQueryModel != null)
{
feed.NextPageLink = GetNextPageLink(originalQueryModel);
}
feedWriter.WriteStart(feed);
foreach (var entry in entries)
{
feedWriter.WriteStart(entry);
feedWriter.WriteEnd();
}
feedWriter.WriteEnd();
feedWriter.Flush();
}
