/*
* Copyright Aduna (http://www.aduna-software.com/) (c) 2007.
*
* Licensed under the Aduna BSD-style license.
*/
package org.openrdf.rio.trig;
import java.io.IOException;
import java.io.OutputStream;
import java.io.Writer;
import org.openrdf.model.Resource;
import org.openrdf.model.Statement;
import org.openrdf.rio.RDFFormat;
import org.openrdf.rio.RDFHandlerException;
import org.openrdf.rio.turtle.TurtleWriter;
/**
* An extension of {@link TurtleWriter} that writes RDF documents in <a
* href="http://www.wiwiss.fu-berlin.de/suhl/bizer/TriG/Spec/">TriG</a> format
* by adding graph scopes to the Turtle document.
*
* @author Arjohn Kampman
*/
public class TriGWriter extends TurtleWriter {
/*-----------*
* Variables *
*-----------*/
private boolean inActiveContext;
private Resource currentContext;
/*--------------*
* Constructors *
*--------------*/
/**
* Creates a new TriGWriter that will write to the supplied OutputStream.
*
* @param out
* The OutputStream to write the TriG document to.
*/
public TriGWriter(OutputStream out) {
super(out);
}
/**
* Creates a new TriGWriter that will write to the supplied Writer.
*
* @param writer
* The Writer to write the TriG document to.
*/
public TriGWriter(Writer writer) {
super(writer);
}
/*---------*
* Methods *
*---------*/
@Override
public RDFFormat getRDFFormat() {
return RDFFormat.TRIG;
}
@Override
public void startRDF()
throws RDFHandlerException
{
super.startRDF();
inActiveContext = false;
currentContext = null;
}
@Override
public void endRDF()
throws RDFHandlerException
{
super.endRDF();
try {
closeActiveContext();
writer.flush();
}
catch (IOException e) {
throw new RDFHandlerException(e);
}
}
@Override
public void handleStatement(Statement st)
throws RDFHandlerException
{
if (!writingStarted) {
throw new RuntimeException("Document writing has not yet been started");
}
try {
Resource context = st.getContext();
if (inActiveContext && !contextsEquals(context, currentContext)) {
closePreviousStatement();
closeActiveContext();
}
if (!inActiveContext) {
writer.writeEOL();
if (context != null) {
writeResource(context);
writer.write(" ");
}
writer.write("{");
writer.increaseIndentation();
currentContext = context;
inActiveContext = true;
}
}
catch (IOException e) {
throw new RDFHandlerException(e);
}
super.handleStatement(st);
}
@Override
protected void writeCommentLine(String line)
throws IOException
{
closeActiveContext();
super.writeCommentLine(line);
}
@Override
protected void writeNamespace(String prefix, String name)
throws IOException
{
closeActiveContext();
super.writeNamespace(prefix, name);
}
protected void closeActiveContext()
throws IOException
{
if (inActiveContext) {
writer.decreaseIndentation();
writer.write("}");
writer.writeEOL();
inActiveContext = false;
currentContext = null;
}
}
private static final boolean contextsEquals(Resource context1, Resource context2) {
if (context1 == null) {
return context2 == null;
}
else {
return context1.equals(context2);
}
}
}