/// <summary>
/// Processes a POST operation which adds triples to a new Graph in the Store and returns the URI of the newly created Graph
/// </summary>
/// <param name="context">HTTP Context</param>
/// <remarks>
/// <para>
/// This operation allows clients to POST data to an endpoint and have it create a Graph and assign a URI for them.
/// </para>
/// </remarks>
public override void ProcessPostCreate(HttpContext context)
{
//Get the payload assuming there is one
IGraph g = this.ParsePayload(context);
//Mint a URI for the Graph
Uri graphUri = this.MintGraphUri(context, g);
//First generate a CREATE to ensure that the Graph exists
//We don't do a CREATE SILENT as this operation is supposed to generate a new Graph URI
//so if MintGraphUri() fails to deliver a unused Graph URI then the operation should fail
StringBuilder insert = new StringBuilder();
insert.AppendLine("CREATE GRAPH @graph ;");
//Then Generate an INSERT DATA command for the actual POST
//Note that if the payload is empty this still has the effect of creating a Graph
if (g != null)
{
insert.AppendLine("INSERT DATA { GRAPH @graph {");
TurtleFormatter formatter = new TurtleFormatter(g.NamespaceMap);
foreach (Triple t in g.Triples)
{
insert.AppendLine(t.ToString(formatter));
}
insert.AppendLine("} }");
}
//Parse and evaluate the command
SparqlParameterizedString insertCmd = new SparqlParameterizedString(insert.ToString());
insertCmd.Namespaces = g.NamespaceMap;
insertCmd.SetUri("graph", graphUri);
SparqlUpdateCommandSet cmds = this._parser.ParseFromString(insertCmd);
this._updateProcessor.ProcessCommandSet(cmds);
this._updateProcessor.Flush();
//Finally return a 201 Created and a Location header with the new Graph URI
context.Response.StatusCode = (int)HttpStatusCode.Created;
try
{
context.Response.Headers.Add("Location", graphUri.ToString());
}
catch (PlatformNotSupportedException)
{
context.Response.AddHeader("Location", graphUri.ToString());
}
}
/// <summary>
/// Processes a PUT operation
/// </summary>
/// <param name="context">HTTP Context</param>
public override void ProcessPut(HttpContext context)
{
//Get the payload assuming there is one
IGraph g = this.ParsePayload(context);
//Get the Graph URI of the Graph to be added
Uri graphUri = this.ResolveGraphUri(context, g);
//Determine whether the Graph already exists or not, if it doesn't then we have to send a 201 Response
bool created = false;
try
{
SparqlQueryParser parser = new SparqlQueryParser();
SparqlParameterizedString graphExistsQuery = new SparqlParameterizedString();
graphExistsQuery.CommandText = "ASK WHERE { GRAPH @graph { } }";
graphExistsQuery.SetUri("graph", graphUri);
Object temp = this._queryProcessor.ProcessQuery(parser.ParseFromString(graphExistsQuery));
if (temp is SparqlResultSet)
{
created = !((SparqlResultSet)temp).Result;
}
}
catch
{
//If any error occurs assume the Graph doesn't exist and so we'll return a 201 created
created = true;
}
//Generate a set of commands based upon this
StringBuilder cmdSequence = new StringBuilder();
if (graphUri != null)
{
cmdSequence.AppendLine("DROP SILENT GRAPH @graph ;");
cmdSequence.Append("CREATE SILENT GRAPH @graph");
}
else
{
cmdSequence.Append("DROP SILENT DEFAULT");
}
if (g != null)
{
cmdSequence.AppendLine(" ;");
if (graphUri != null)
{
cmdSequence.AppendLine("INSERT DATA { GRAPH @graph {");
}
else
{
cmdSequence.AppendLine("INSERT DATA { ");
}
TurtleFormatter formatter = new TurtleFormatter(g.NamespaceMap);
foreach (Triple t in g.Triples)
{
cmdSequence.AppendLine(t.ToString(formatter));
}
if (graphUri != null)
{
cmdSequence.AppendLine("} }");
}
else
{
cmdSequence.AppendLine("}");
}
}
SparqlParameterizedString put = new SparqlParameterizedString(cmdSequence.ToString());
put.Namespaces = g.NamespaceMap;
if (graphUri != null) put.SetUri("graph", graphUri);
SparqlUpdateCommandSet putCmds = this._parser.ParseFromString(put);
this._updateProcessor.ProcessCommandSet(putCmds);
this._updateProcessor.Flush();
//Return a 201 if required, otherwise the default behaviour of returning a 200 will occur automatically
if (created)
{
context.Response.StatusCode = (int)HttpStatusCode.Created;
}
}
/// <summary>
/// Processes a POST operation
/// </summary>
/// <param name="context">HTTP Context</param>
public override void ProcessPost(HttpContext context)
{
//Get the payload assuming there is one
IGraph g = this.ParsePayload(context);
if (g == null)
{
//Q: What should the behaviour be when the payload is null for a POST? Assuming a 200 OK response
return;
}
//Get the Graph URI of the Graph to be added
Uri graphUri = this.ResolveGraphUri(context, g);
//First we need a
//Generate an INSERT DATA command for the POST
StringBuilder insert = new StringBuilder();
if (graphUri != null)
{
insert.AppendLine("INSERT DATA { GRAPH @graph {");
}
else
{
insert.AppendLine("INSERT DATA {");
}
TurtleFormatter formatter = new TurtleFormatter(g.NamespaceMap);
foreach (Triple t in g.Triples)
{
insert.AppendLine(t.ToString(formatter));
}
if (graphUri != null)
{
insert.AppendLine("} }");
}
else
{
insert.AppendLine("}");
}
//Parse and evaluate the command
SparqlParameterizedString insertCmd = new SparqlParameterizedString(insert.ToString());
insertCmd.Namespaces = g.NamespaceMap;
if (graphUri != null) insertCmd.SetUri("graph", graphUri);
SparqlUpdateCommandSet cmds = this._parser.ParseFromString(insertCmd);
this._updateProcessor.ProcessCommandSet(cmds);
this._updateProcessor.Flush();
}
