/// <summary>
/// Processes a HEAD operation
/// </summary>
/// <param name="context">HTTP Context</param>
public override void ProcessHead(IHttpContext context)
{
// Work out the Graph URI we want to get
Uri graphUri = this.ResolveGraphUri(context);
try
{
bool exists = this.HasGraph(graphUri);
if (exists)
{
// Send the Content Type we'd select based on the Accept header to the user
String ctype;
IRdfWriter writer = MimeTypesHelper.GetWriter(context.GetAcceptTypes(), out ctype);
context.Response.ContentType = ctype;
}
else
{
context.Response.StatusCode = (int)HttpStatusCode.NotFound;
}
}
catch (RdfQueryException)
{
// If the GetGraph() method errors this implies that the Store does not contain the Graph
// In such a case we should return a 404
context.Response.StatusCode = (int)HttpStatusCode.NotFound;
return;
}
}
/// <summary>
/// Sends the given Graph to the Client via the HTTP Response.
/// </summary>
/// <param name="context">HTTP Context.</param>
/// <param name="g">Graph to send.</param>
protected void SendResultsToClient(IHttpContext context, IGraph g)
{
IRdfWriter writer;
String ctype;
// Look up the MIME Type Definition - if none use GetWriter instead
MimeTypeDefinition definition = MimeTypesHelper.GetDefinitions(context.GetAcceptTypes()).FirstOrDefault(d => d.CanWriteRdf);
if (definition != null)
{
writer = definition.GetRdfWriter();
ctype = definition.CanonicalMimeType;
}
else
{
writer = MimeTypesHelper.GetWriter(context.GetAcceptTypes(), out ctype);
}
// Set up the Writer
if (writer is ICompressingWriter)
{
((ICompressingWriter)writer).CompressionLevel = Options.DefaultCompressionLevel;
}
// Send Content to Client
context.Response.ContentType = ctype;
if (definition != null)
{
context.Response.ContentEncoding = definition.Encoding;
writer.Save(g, new StreamWriter(context.Response.OutputStream, definition.Encoding));
}
else
{
writer.Save(g, new StreamWriter(context.Response.OutputStream));
}
}
/// <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(IHttpContext context, Object result, BaseHandlerConfiguration config)
{
MimeTypeDefinition definition = null;
String ctype = "text/plain";
String[] acceptTypes = context.GetAcceptTypes();
// Return the Results
if (result is SparqlResultSet)
{
ISparqlResultsWriter sparqlWriter = null;
// Try and get a MIME Type Definition using the HTTP Requests Accept Header
if (acceptTypes != null)
{
definition = MimeTypesHelper.GetDefinitions(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);
// Clear any existing Response
context.Response.Clear();
// Send Result Set to Client
context.Response.ContentEncoding = definition.Encoding;
sparqlWriter.Save((SparqlResultSet)result, new StreamWriter(context.Response.OutputStream, definition.Encoding));
}
else if (result is IGraph)
{
IRdfWriter rdfWriter = null;
// Try and get a MIME Type Definition using the HTTP Requests Accept Header
if (acceptTypes != null)
{
definition = MimeTypesHelper.GetDefinitions(acceptTypes).FirstOrDefault(d => d.CanWriteRdf);
}
if (definition == null)
{
// If no appropriate definition then use the GetWriter method instead
rdfWriter = MimeTypesHelper.GetWriter(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.ContentEncoding = definition.Encoding;
rdfWriter.Save((IGraph)result, new StreamWriter(context.Response.OutputStream, definition.Encoding));
}
else
{
rdfWriter.Save((IGraph)result, new StreamWriter(context.Response.OutputStream));
}
}
else if (result is ITripleStore)
{
IStoreWriter storeWriter = null;
// Try and get a MIME Type Definition using the HTTP Requests Accept Header
if (acceptTypes != null)
{
definition = MimeTypesHelper.GetDefinitions(acceptTypes).FirstOrDefault(d => d.CanWriteRdfDatasets);
}
if (definition == null)
{
// If no appropriate definition then use the GetStoreWriter method instead
storeWriter = MimeTypesHelper.GetStoreWriter(acceptTypes, out ctype);
}
else
{
storeWriter = definition.GetRdfDatasetWriter();
}
// Setup the writer
if (definition != null)
{
ctype = definition.CanonicalMimeType;
}
context.Response.ContentType = ctype;
HandlerHelper.ApplyWriterOptions(storeWriter, config);
// Clear any existing Response
context.Response.Clear();
// Send Triple Store to Client
if (definition != null)
{
context.Response.ContentEncoding = definition.Encoding;
storeWriter.Save((ITripleStore)result, new StreamWriter(context.Response.OutputStream, definition.Encoding));
}
else
{
storeWriter.Save((ITripleStore)result, new StreamWriter(context.Response.OutputStream));
}
}
else if (result is ISparqlDataset)
{
// Wrap in a Triple Store and then call self so the Triple Store writing branch of this if gets called instead
TripleStore store = new TripleStore(new DatasetGraphCollection((ISparqlDataset)result));
HandlerHelper.SendToClient(context, store, config);
}
else
{
throw new RdfOutputException("Unexpected Result Object of Type '" + result.GetType().ToString() + "' returned - unable to write Objects of this Type to the HTTP Response");
}
}
