package de.fuberlin.wiwiss.pubby;
import java.io.IOException;
import java.io.OutputStreamWriter;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.rdf.model.RDFWriter;
import com.hp.hpl.jena.shared.JenaException;
import de.fuberlin.wiwiss.pubby.negotiation.ContentTypeNegotiator;
import de.fuberlin.wiwiss.pubby.negotiation.MediaRangeSpec;
import de.fuberlin.wiwiss.pubby.negotiation.PubbyNegotiator;
import de.fuberlin.wiwiss.pubby.servlets.RequestParamHandler;
/**
* Calls into Joseki to send a Jena model over HTTP. This gives us
* content negotiation and all the other tricks supported by Joseki
* for free. This has to be in the Joseki package because some
* required methods are not visible.
*/
public class ModelResponse {
private final Model model;
private final HttpServletRequest request;
private final HttpServletResponse response;
public ModelResponse(Model model, HttpServletRequest request,
HttpServletResponse response) {
// Handle ?output=format request parameter
RequestParamHandler handler = new RequestParamHandler(request);
if (handler.isMatchingRequest()) {
request = handler.getModifiedRequest();
}
this.model = model;
this.request = request;
this.response = response;
}
public void serve() {
// Error hendling is still quite a mess here.
try {
doResponseModel();
} catch (IOException ioEx) {
throw new RuntimeException(ioEx);
} catch (JenaException jEx) {
try {
response.sendError(
HttpServletResponse.SC_INTERNAL_SERVER_ERROR,
"JenaException: " + jEx.getMessage());
} catch (IOException e) {
throw new RuntimeException(e);
}
}
}
private void doResponseModel() throws IOException {
response.addHeader("Vary", "Accept");
ContentTypeNegotiator negotiator = PubbyNegotiator.getDataNegotiator();
MediaRangeSpec bestMatch = negotiator.getBestMatch(
request.getHeader("Accept"), request.getHeader("User-Agent"));
if (bestMatch == null) {
response.setStatus(406);
response.setContentType("text/plain");
ServletOutputStream out = response.getOutputStream();
out.println("406 Not Acceptable: The requested data format is not supported.");
out.println("Supported formats are RDF/XML, Turtle, N3, and N-Triples.");
return;
}
response.setContentType(bestMatch.getMediaType());
getWriter(bestMatch.getMediaType()).write(model, response);
response.getOutputStream().flush();
}
private ModelWriter getWriter(String mediaType) {
if ("application/rdf+xml".equals(mediaType)) {
return new RDFXMLWriter();
}
if ("application/x-turtle".equals(mediaType)) {
return new TurtleWriter();
}
if ("text/rdf+n3;charset=utf-8".equals(mediaType)) {
return new TurtleWriter();
}
return new NTriplesWriter();
}
private interface ModelWriter {
void write(Model model, HttpServletResponse response) throws IOException;
}
private class NTriplesWriter implements ModelWriter {
public void write(Model model, HttpServletResponse response) throws IOException {
model.getWriter("N-TRIPLES").write(model, response.getOutputStream(), null);
}
}
private class TurtleWriter implements ModelWriter {
public void write(Model model, HttpServletResponse response) throws IOException {
model.getWriter("TURTLE").write(model, response.getOutputStream(), null);
}
}
private class RDFXMLWriter implements ModelWriter {
public void write(Model model, HttpServletResponse response) throws IOException {
RDFWriter writer = model.getWriter("RDF/XML-ABBREV");
writer.setProperty("showXmlDeclaration", "true");
// From Joseki -- workaround for the j.cook.up bug.
writer.setProperty("blockRules", "propertyAttr");
writer.write(model,
new OutputStreamWriter(response.getOutputStream(), "utf-8"), null);
}
}
}