/// <summary>
/// Processes a SPARQL Query Request
/// </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);
if (context.Request.HttpMethod.Equals("OPTIONS"))
{
//OPTIONS requests always result in the Service Description document
IGraph svcDescrip = SparqlServiceDescriber.GetServiceDescription(context, this._config, new Uri(context.Request.Url.AbsoluteUri));
HandlerHelper.SendToClient(context, svcDescrip, this._config);
return;
}
//See if there has been an query submitted
String queryText = context.Request.QueryString["query"];
if (queryText == null || queryText.Equals(String.Empty))
{
queryText = context.Request.Form["query"];
}
//If no Query sent either show Query Form or give a HTTP 400 response
if (queryText == null || queryText.Equals(String.Empty))
{
//If there is no Query we may return the SPARQL Service Description where appropriate
try
{
//If we might show the Query Form only show the Description if the selected writer is
//not a HTML writer
MimeTypeDefinition definition = MimeTypesHelper.GetDefinitions(HandlerHelper.GetAcceptTypes(context)).FirstOrDefault(d => d.CanWriteRdf);
if (definition != null)
{
IRdfWriter writer = definition.GetRdfWriter();
if (!this._config.ShowQueryForm || !(writer is IHtmlWriter))
{
//If not a HTML Writer selected OR not showing Query Form then show the Service Description Graph
//unless an error occurs creating it
IGraph serviceDescrip = SparqlServiceDescriber.GetServiceDescription(context, this._config, new Uri(context.Request.Url.AbsoluteUri));
context.Response.ContentType = definition.CanonicalMimeType;
context.Response.ContentEncoding = definition.Encoding;
writer.Save(serviceDescrip, new StreamWriter(context.Response.OutputStream, definition.Encoding));
return;
}
}
}
catch
{
//Ignore Exceptions - we'll just show the Query Form or return a 400 Bad Request instead
}
//If a Writer can't be selected then we'll either show the Query Form or return a 400 Bad Request
if (this._config.ShowQueryForm)
{
this.ShowQueryForm(context);
}
else
{
context.Response.StatusCode = (int)HttpStatusCode.BadRequest;
}
return;
}
//Get Other options associated with this query
List<String> userDefaultGraphs = new List<String>();
List<String> userNamedGraphs = new List<String>();
long timeout = 0;
bool partialResults = this._config.DefaultPartialResults;
//Get the Default Graph URIs (if any)
if (context.Request.QueryString["default-graph-uri"] != null)
{
userDefaultGraphs.AddRange(context.Request.QueryString.GetValues("default-graph-uri"));
}
else if (context.Request.Form["default-graph-uri"] != null)
{
userDefaultGraphs.AddRange(context.Request.Form.GetValues("default-graph-uri"));
}
//Get the Named Graph URIs (if any)
if (context.Request.QueryString["named-graph-uri"] != null)
{
userNamedGraphs.AddRange(context.Request.QueryString.GetValues("named-graph-uri"));
}
else if (context.Request.Form["named-graph-uri"] != null)
{
userNamedGraphs.AddRange(context.Request.Form.GetValues("named-graph-uri"));
}
//Get Timeout setting (if any)
if (context.Request.QueryString["timeout"] != null)
{
if (!Int64.TryParse(context.Request.QueryString["timeout"], out timeout))
{
timeout = this._config.DefaultTimeout;
}
}
else if (context.Request.Form["timeout"] != null)
{
if (!Int64.TryParse(context.Request.Form["timeout"], out timeout))
{
timeout = this._config.DefaultTimeout;
}
}
//Get Partial Results Setting (if any);
if (context.Request.QueryString["partialResults"] != null)
{
if (!Boolean.TryParse(context.Request.QueryString["partialResults"], out partialResults))
{
partialResults = this._config.DefaultPartialResults;
}
}
else if (context.Request.Form["partialResults"] != null)
{
if (!Boolean.TryParse(context.Request.Form["partialResults"], out partialResults))
{
partialResults = this._config.DefaultPartialResults;
}
}
try
{
//Now we're going to parse the Query
SparqlQueryParser parser = new SparqlQueryParser(this._config.Syntax);
parser.ExpressionFactories = this._config.ExpressionFactories;
parser.QueryOptimiser = this._config.QueryOptimiser;
SparqlQuery query = parser.ParseFromString(queryText);
query.AlgebraOptimisers = this._config.AlgebraOptimisers;
//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, requireActionAuth = false;
if (this._config.UserGroups.Any())
{
//If we have user
isAuth = HandlerHelper.IsAuthenticated(context, this._config.UserGroups);
requireActionAuth = true;
}
if (!isAuth) return;
//Is this user allowed to make this kind of query?
if (requireActionAuth) HandlerHelper.IsAuthenticated(context, this._config.UserGroups, this.GetPermissionAction(query));
//Set the Default Graph URIs (if any)
if (userDefaultGraphs.Count > 0)
{
//Default Graph Uri specified by default-graph-uri parameter or Web.config settings
foreach (String userDefaultGraph in userDefaultGraphs)
{
if (!userDefaultGraph.Equals(String.Empty))
{
query.AddDefaultGraph(new Uri(userDefaultGraph));
}
}
}
else if (!this._config.DefaultGraphURI.Equals(String.Empty))
{
//Only applies if the Query doesn't specify any Default Graph
if (!query.DefaultGraphs.Any())
{
query.AddDefaultGraph(new Uri(this._config.DefaultGraphURI));
}
}
//Set the Named Graph URIs (if any)
if (userNamedGraphs.Count > 0)
{
foreach (String userNamedGraph in userNamedGraphs)
{
if (!userNamedGraph.Equals(String.Empty))
{
query.AddNamedGraph(new Uri(userNamedGraph));
}
}
}
//Set Timeout setting
if (timeout > 0)
{
query.Timeout = timeout;
}
else
{
query.Timeout = this._config.DefaultTimeout;
}
//Set Partial Results Setting
query.PartialResultsOnTimeout = partialResults;
//Set Describe Algorithm
query.Describer = this._config.DescribeAlgorithm;
//Now we can finally make the query and return the results
Object result = this.ProcessQuery(query);
this.ProcessResults(context, result);
//Update the Cache as the request may have changed the endpoint
this.UpdateConfig(context);
}
catch (RdfParseException parseEx)
{
HandleErrors(context, "Parsing Error", queryText, parseEx, (int)HttpStatusCode.BadRequest);
}
catch (RdfQueryTimeoutException timeoutEx)
{
HandleErrors(context, "Query Timeout Error", queryText, timeoutEx);
}
catch (RdfQueryException queryEx)
{
HandleErrors(context, "Update Error", queryText, queryEx);
}
catch (RdfWriterSelectionException writerSelEx)
{
HandleErrors(context, "Output Selection Error", queryText, writerSelEx, (int)HttpStatusCode.NotAcceptable);
}
catch (RdfException rdfEx)
{
HandleErrors(context, "RDF Error", queryText, rdfEx);
}
catch (Exception ex)
{
HandleErrors(context, "Error", queryText, ex);
}
}
/// <summary>
/// Generates a SPARQL Service Description Graph for the given Query Handler Configuration or uses the configuration supplied Description Graph
/// </summary>
/// <param name="context">HTTP Context</param>
/// <param name="config">Query Handler Configuration</param>
/// <param name="descripUri">Base URI of the Description</param>
/// <returns></returns>
public static IGraph GetServiceDescription(HttpContext context, BaseQueryHandlerConfiguration config, Uri descripUri)
{
//Use user specified Service Description if present
if (config.ServiceDescription != null) return config.ServiceDescription;
IGraph g = SparqlServiceDescriber.GetNewGraph();
//Add the Top Level Node representing the Service
IUriNode descrip = g.CreateUriNode(descripUri);
IUriNode rdfType = g.CreateUriNode(new Uri(RdfSpecsHelper.RdfType));
IUriNode service = g.CreateUriNode("sd:" + ClassService);
g.Assert(descrip, rdfType, service);
//Add its sd:url
IUriNode url = g.CreateUriNode("sd:" + PropertyUrl);
g.Assert(descrip, url, descrip);
//Add the sd:supportedLanguage - Requires Query Language to be configurable through the Configuration API
IUriNode supportedLang = g.CreateUriNode("sd:" + PropertySupportedLanguage);
IUriNode lang;
switch (config.Syntax)
{
case SparqlQuerySyntax.Extended:
case SparqlQuerySyntax.Sparql_1_1:
lang = g.CreateUriNode("sd:" + InstanceSparql11Query);
break;
default:
lang = g.CreateUriNode("sd:" + InstanceSparql10Query);
break;
}
g.Assert(descrip, supportedLang, lang);
//Add the Result Formats
IUriNode resultFormat = g.CreateUriNode("sd:" + PropertyResultFormat);
foreach (MimeTypeDefinition definition in MimeTypesHelper.Definitions)
{
if (definition.CanWriteRdf || definition.CanWriteSparqlResults)
{
if (definition.FormatUri != null)
{
g.Assert(descrip, resultFormat, g.CreateUriNode(new Uri(definition.FormatUri)));
}
}
}
//Add Features and Dataset Description
//First add descriptions for Global Expression Factories
IUriNode extensionFunction = g.CreateUriNode("sd:" + PropertyExtensionFunction);
IUriNode extensionAggregate = g.CreateUriNode("sd:" + PropertyExtensionAggregate);
foreach (ISparqlCustomExpressionFactory factory in SparqlExpressionFactory.Factories)
{
foreach (Uri u in factory.AvailableExtensionFunctions)
{
g.Assert(descrip, extensionFunction, g.CreateUriNode(u));
}
foreach (Uri u in factory.AvailableExtensionAggregates)
{
g.Assert(descrip, extensionAggregate, g.CreateUriNode(u));
}
}
//Then get the Configuration Object to add any other Feature Descriptions it wishes to
config.AddFeatureDescription(g, descrip);
return g;
}
