public async Task <SparqlQueryResult> ExecuteQueryAsync(string expr, CancellationToken ct)
{
if (expr == null)
{
throw new ArgumentNullException(nameof(expr));
}
ct.ThrowIfCancellationRequested();
var loadedGraph = await EnsureGraphLoadedAsync();
if (expr == null)
{
throw new ArgumentNullException(nameof(expr));
}
ct.ThrowIfCancellationRequested();
var sw = Stopwatch.StartNew();
using (logger.BeginScope("ExprHash={ExprHash}", expr.GetHashCode()))
{
try
{
logger.LogInformation("Start execute query; ExprLength={ExprLength}.", expr.Length);
var queryStr = new SparqlParameterizedString(expr);
foreach (var prefix in loadedGraph.Graph.NamespaceMap.Prefixes)
{
if (!queryStr.Namespaces.HasNamespace(prefix))
{
queryStr.Namespaces.AddNamespace(prefix, loadedGraph.Graph.NamespaceMap.GetNamespaceUri(prefix));
}
}
var query = queryParser.ParseFromString(queryStr);
logger.LogDebug("Parsed query. Elapsed time: {Elapsed}.", sw.Elapsed);
query.Timeout = (int)options.QueryTimeout.TotalMilliseconds;
query.Limit = options.ResultLimit;
ct.ThrowIfCancellationRequested();
var weakResult = loadedGraph.QueryProcessor.ProcessQuery(query);
// returns either a SparqlResultSet or an IGraph instance
if (weakResult is IGraph)
{
logger.LogWarning("Query result is IGraph.");
}
var result = new SparqlQueryResult(weakResult);
logger.LogInformation("Executed query with {Results} {ResultType} results. Elapsed time: {Elapsed}.",
result.RecordsCount, result.ResultType, sw.Elapsed);
return(result);
}
catch (Exception ex)
{
logger.LogError(ex, "Error during executing query. Elapsed time: {Elapsed}.", sw.Elapsed);
throw;
}
}
}
// See https://github.com/dotnetrdf/dotnetrdf/blob/5b7fc480346c90eb9b164fb4f8ee09f378442d52/Libraries/dotNetRDF.Web/HandlerHelper.cs#L157
/// <summary>
/// Helper function which returns the Results (Graph/Triple Store/SPARQL Results) back to the Client in one of their accepted formats
/// </summary>
/// <param name="context">Context of the HTTP Request</param>
/// <param name="result">Results of the Sparql Query</param>
/// <param name="config">Handler Configuration</param>
public static void SendToClient(HttpContext context, SparqlQueryResult result)
{
MimeTypeDefinition definition = null;
const string TEXT_PLAIN = "text/plain";
var acceptTypes = context.Request.Headers[HeaderNames.Accept];
// Return the Results
if (result.SparqlResultSet != null)
{
ISparqlResultsWriter sparqlWriter = null;
// Try and get a MIME Type Definition using the HTTP Requests Accept Header
if (acceptTypes.Count > 0)
{
definition = MimeTypesHelper.GetDefinitions((IEnumerable <string>)acceptTypes).FirstOrDefault(d => d.CanWriteSparqlResults);
}
// Try and get the registered Definition for SPARQL Results XML
if (definition == null)
{
definition = MimeTypesHelper.GetDefinitions(MimeTypesHelper.SparqlResultsXml[0]).FirstOrDefault();
}
// If Definition is still null create a temporary definition
if (definition == null)
{
definition = new MimeTypeDefinition("SPARQL Results XML", MimeTypesHelper.SparqlResultsXml, Enumerable.Empty <String>());
definition.SparqlResultsWriterType = typeof(VDS.RDF.Writing.SparqlXmlWriter);
}
// Set up the Writer appropriately
sparqlWriter = definition.GetSparqlResultsWriter();
context.Response.ContentType = definition.CanonicalMimeType;
// HandlerHelper.ApplyWriterOptions(sparqlWriter, config);
// Send Result Set to Client
context.Response.Headers[HeaderNames.ContentEncoding] = definition.Encoding.WebName;
sparqlWriter.Save(result.SparqlResultSet, new StreamWriter(context.Response.Body, definition.Encoding));
}
else if (result.Graph != null)
{
IRdfWriter rdfWriter = null;
var ctype = TEXT_PLAIN;
// Try and get a MIME Type Definition using the HTTP Requests Accept Header
if (acceptTypes.Count > 0)
{
definition = MimeTypesHelper.GetDefinitions((IEnumerable <string>)acceptTypes).FirstOrDefault(d => d.CanWriteRdf);
}
if (definition == null)
{
// If no appropriate definition then use the GetWriter method instead
rdfWriter = MimeTypesHelper.GetWriter((IEnumerable <string>)acceptTypes, out ctype);
}
else
{
rdfWriter = definition.GetRdfWriter();
}
// Setup the writer
if (definition != null)
{
ctype = definition.CanonicalMimeType;
}
context.Response.ContentType = ctype;
//HandlerHelper.ApplyWriterOptions(rdfWriter, config);
// Clear any existing Response
//context.Response.Clear();
// Send Graph to Client
if (definition != null)
{
context.Response.Headers[HeaderNames.ContentEncoding] = definition.Encoding.WebName;
rdfWriter.Save(result.Graph, new StreamWriter(context.Response.Body, definition.Encoding));
}
else
{
rdfWriter.Save(result.Graph, new StreamWriter(context.Response.Body));
}
}
else
{
Debug.Assert(result == SparqlQueryResult.Null);
}
}
