/// <summary>
/// Processes the request by loading the Configuration in order to obtain the Graph to be served and then serving it to the client
/// </summary>
/// <param name="context">HTTP Context</param>
public void ProcessRequest(HttpContext context)
{
this._config = this.LoadConfig(context);
//Add our Standard Headers
HandlerHelper.AddStandardHeaders(context, this._config);
//Check whether we need to use authentication
//If there are no user groups then no authentication is in use so we default to authenticated with no per-action authentication needed
bool isAuth = true;
if (this._config.UserGroups.Any())
{
//If we have user
isAuth = HandlerHelper.IsAuthenticated(context, this._config.UserGroups);
}
if (!isAuth)
{
return;
}
//Check whether we can just send a 304 Not Modified
if (HandlerHelper.CheckCachingHeaders(context, this._config.ETag, null))
{
context.Response.StatusCode = (int)HttpStatusCode.NotModified;
HandlerHelper.AddCachingHeaders(context, this._config.ETag, null);
return;
}
try
{
String[] acceptTypes = HandlerHelper.GetAcceptTypes(context);
//Retrieve an appropriate MIME Type Definition which can be used to get a Writer
MimeTypeDefinition definition = MimeTypesHelper.GetDefinitions(acceptTypes).FirstOrDefault(d => d.CanWriteRdf);
if (definition == null)
{
throw new RdfWriterSelectionException("No MIME Type Definitions have a registered RDF Writer for the MIME Types specified in the HTTP Accept Header");
}
IRdfWriter writer = this.SelectWriter(definition);
HandlerHelper.ApplyWriterOptions(writer, this._config);
IGraph g = this.ProcessGraph(this._config.Graph);
if (this._config.ETag == null)
{
this._config.ETag = this.ComputeETag(g);
}
//Serve the Graph to the User
context.Response.ContentType = definition.CanonicalMimeType;
HandlerHelper.AddCachingHeaders(context, this._config.ETag, null);
if (writer is IHtmlWriter)
{
if (!this._config.Stylesheet.Equals(String.Empty))
{
((IHtmlWriter)writer).Stylesheet = this._config.Stylesheet;
}
}
context.Response.ContentEncoding = definition.Encoding;
HandlerHelper.ApplyWriterOptions(writer, this._config);
writer.Save(g, new StreamWriter(context.Response.OutputStream, definition.Encoding));
this.UpdateConfig(context);
}
catch (RdfWriterSelectionException)
{
context.Response.StatusCode = (int)HttpStatusCode.NotAcceptable;
}
catch
{
context.Response.StatusCode = (int)HttpStatusCode.InternalServerError;
}
}
/// <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, Object result, BaseHandlerConfiguration config)
{
MimeTypeDefinition definition = null;
String ctype = "text/plain";
String[] acceptTypes = HandlerHelper.GetAcceptTypes(context);
//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.SparqlXml[0]).FirstOrDefault();
}
//If Definition is still null create a temporary definition
if (definition == null)
{
definition = new MimeTypeDefinition("SPARQL Results XML", MimeTypesHelper.SparqlXml, 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 VDS.RDF.Storage.Params.StreamParams(context.Response.OutputStream, definition.Encoding));
}
else
{
storeWriter.Save((ITripleStore)result, new VDS.RDF.Storage.Params.StreamParams(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");
}
}
