/// <summary>
/// Evaluates the subquery in the given context.
/// </summary>
/// <param name="context">Evaluation Context.</param>
/// <returns></returns>
public BaseMultiset Evaluate(SparqlEvaluationContext context)
{
// Use the same algebra optimisers as the parent query (if any)
if (context.Query != null)
{
_subquery.AlgebraOptimisers = context.Query.AlgebraOptimisers;
}
if (context.InputMultiset is NullMultiset)
{
context.OutputMultiset = context.InputMultiset;
}
else if (context.InputMultiset.IsEmpty)
{
context.OutputMultiset = new NullMultiset();
}
else
{
SparqlEvaluationContext subcontext = new SparqlEvaluationContext(_subquery, context.Data, context.Processor);
// Add any Named Graphs to the subquery
if (context.Query != null)
{
foreach (Uri u in context.Query.NamedGraphs)
{
_subquery.AddNamedGraph(u);
}
}
ISparqlAlgebra query = _subquery.ToAlgebra();
try
{
// Evaluate the Subquery
context.OutputMultiset = subcontext.Evaluate(query);
// If the Subquery contains a GROUP BY it may return a Group Multiset in which case we must flatten this to a Multiset
if (context.OutputMultiset is GroupMultiset)
{
context.OutputMultiset = new Multiset((GroupMultiset)context.OutputMultiset);
}
// Strip out any Named Graphs from the subquery
if (_subquery.NamedGraphs.Any())
{
_subquery.ClearNamedGraphs();
}
}
catch (RdfQueryException queryEx)
{
throw new RdfQueryException("Query failed due to a failure in Subquery Execution:\n" + queryEx.Message, queryEx);
}
}
return(context.OutputMultiset);
}
/// <summary>
/// Processes a SPARQL Query Request
/// </summary>
/// <param name="context">HTTP Context</param>
public void ProcessRequest(HttpContext context)
{
this._config = this.LoadConfig(context);
WebContext webContext = new WebContext(context);
//Add our Standard Headers
HandlerHelper.AddStandardHeaders(webContext, this._config);
//Options we need to determine based on the HTTP Method used
String[] queries;
String queryText = null;
List <String> userDefaultGraphs = new List <String>();
List <String> userNamedGraphs = new List <String>();
try
{
//Decide what to do based on the HTTP Method
switch (context.Request.HttpMethod.ToUpper())
{
case "OPTIONS":
//OPTIONS requests always result in the Service Description document
IGraph svcDescrip = SparqlServiceDescriber.GetServiceDescription(this._config, UriFactory.Create(context.Request.Url.AbsoluteUri));
HandlerHelper.SendToClient(webContext, svcDescrip, this._config);
return;
case "HEAD":
//Just return from a HEAD request
return;
case "GET":
//GET expects a query parameter in the querystring
queries = context.Request.QueryString.GetValues("query");
if (queries != null)
{
if (queries.Length > 1)
{
throw new ArgumentException("The query parameter was specified multiple times in the querystring");
}
queryText = queries.Length == 1 ? queries[0] : null;
}
//If no Query sent either show Query Form or give a HTTP 400 response
if (String.IsNullOrEmpty(queryText))
{
//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(webContext)).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(this._config, UriFactory.Create(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
}
//Otherwise we'll either show the Query Form or return a 400 Bad Request
if (this._config.ShowQueryForm)
{
this.ShowQueryForm(context);
}
else
{
throw new ArgumentException("Missing required query parameter");
}
return;
}
//Get the Default Graph URIs (if any)
if (context.Request.QueryString["default-graph-uri"] != null)
{
userDefaultGraphs.AddRange(context.Request.QueryString.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"));
}
break;
case "POST":
//POST requires a valid content type
if (context.Request.ContentType != null)
{
MimeTypeSelector contentType = MimeTypeSelector.Create(context.Request.ContentType, 0);
if (contentType.Type.Equals(MimeTypesHelper.WWWFormURLEncoded))
{
//Form URL Encoded was declared type so expect a query parameter in the Form parameters
queries = context.Request.Form.GetValues("query");
if (queries == null)
{
throw new ArgumentException("Required query parameter in POST body was missing");
}
if (queries.Length == 0)
{
throw new ArgumentException("Required query parameter in POST body was missing");
}
if (queries.Length > 1)
{
throw new ArgumentException("The query parameter was specified multiple times in the POST body");
}
queryText = queries[0];
//For Form URL Encoded the Default/Named Graphs may be specified by Form parameters
//Get the Default Graph URIs (if any)
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.Form["named-graph-uri"] != null)
{
userNamedGraphs.AddRange(context.Request.Form.GetValues("named-graph-uri"));
}
break;
}
else if (contentType.Type.Equals(MimeTypesHelper.SparqlQuery))
{
//application/sparql-query was declared type so expect utf-8 charset (if present)
if (contentType.Charset != null && !contentType.Charset.ToLower().Equals(MimeTypesHelper.CharsetUtf8))
{
throw new ArgumentException("HTTP POST request was received with a " + MimeTypesHelper.SparqlQuery + " Content-Type but a non UTF-8 charset parameter");
}
//Read the query from the request body
using (StreamReader reader = new StreamReader(context.Request.InputStream))
{
queryText = reader.ReadToEnd();
reader.Close();
}
//For application/sparql-query the Default/Named Graphs may be specified by querystring parameters
//Get the Default Graph URIs (if any)
if (context.Request.QueryString["default-graph-uri"] != null)
{
userDefaultGraphs.AddRange(context.Request.QueryString.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"));
}
break;
}
else
{
throw new ArgumentException("HTTP POST made to SPARQL query endpoint had an invalid Content-Type header, only " + MimeTypesHelper.WWWFormURLEncoded + " and " + MimeTypesHelper.SparqlQuery + " are acceptable");
}
}
throw new ArgumentException("HTTP POST made to SPARQL Query endpoint was missing the required Content-Type header");
default:
throw new NotSupportedException("HTTP " + context.Request.HttpMethod.ToUpper() + " is not supported by a SPARQL Query endpoint");
}
//Get non-standard options associated with the query
long timeout = 0;
bool partialResults = this._config.DefaultPartialResults;
//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;
}
}
//Now we're going to parse the Query
SparqlQueryParser parser = new SparqlQueryParser(this._config.Syntax);
parser.DefaultBaseUri = context.Request.Url;
parser.ExpressionFactories = this._config.ExpressionFactories;
parser.QueryOptimiser = this._config.QueryOptimiser;
SparqlQuery query = parser.ParseFromString(queryText);
query.AlgebraOptimisers = this._config.AlgebraOptimisers;
query.PropertyFunctionFactories = this._config.PropertyFunctionFactories;
//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(webContext, this._config.UserGroups);
requireActionAuth = true;
}
if (!isAuth)
{
return;
}
//Is this user allowed to make this kind of query?
if (requireActionAuth)
{
HandlerHelper.IsAuthenticated(webContext, this._config.UserGroups, this.GetPermissionAction(query));
}
//Clear query dataset if there is a protocol defined one
userDefaultGraphs.RemoveAll(g => String.IsNullOrEmpty(g));
userNamedGraphs.RemoveAll(g => String.IsNullOrEmpty(g));
bool isProtocolDataset = false;
if (userDefaultGraphs.Count > 0 || userNamedGraphs.Count > 0)
{
query.ClearDefaultGraphs();
query.ClearNamedGraphs();
isProtocolDataset = true;
}
//Set the Default Graph URIs (if any)
if (isProtocolDataset)
{
foreach (String userDefaultGraph in userDefaultGraphs)
{
query.AddDefaultGraph(UriFactory.Create(userDefaultGraph));
}
}
else if (!this._config.DefaultGraphURI.Equals(String.Empty))
{
//Only applies if the Query doesn't specify any Default Graph and there wasn't a protocol defined
//dataset present
if (!query.DefaultGraphs.Any())
{
query.AddDefaultGraph(UriFactory.Create(this._config.DefaultGraphURI));
}
}
//Set the Named Graph URIs (if any)
if (isProtocolDataset)
{
query.ClearNamedGraphs();
foreach (String userNamedGraph in userNamedGraphs)
{
query.AddNamedGraph(UriFactory.Create(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 (NotSupportedException notSupEx)
{
HandleErrors(context, "HTTP Request Error", null, notSupEx, (int)HttpStatusCode.MethodNotAllowed);
}
catch (ArgumentException argEx)
{
HandleErrors(context, "HTTP Request Error", null, argEx, (int)HttpStatusCode.BadRequest);
}
catch (Exception ex)
{
HandleErrors(context, "Error", queryText, ex);
}
}