it.tidalwave.semantic.io.impl.DefaultGraphSerializer Maven / Gradle / Ivy
/***********************************************************************************************************************
*
* blueBill Core - open source birding
* Copyright (C) 2009-2011 by Tidalwave s.a.s. (http://www.tidalwave.it)
*
***********************************************************************************************************************
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
* an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
* specific language governing permissions and limitations under the License.
*
***********************************************************************************************************************
*
* WWW: http://bluebill.tidalwave.it
* SCM: https://kenai.com/hg/bluebill~core-src
*
**********************************************************************************************************************/
package it.tidalwave.semantic.io.impl;
import it.tidalwave.semantic.io.GraphSerializer;
import it.tidalwave.semantic.io.json.JsonPrettyPrinterStream;
import it.tidalwave.semantic.io.json.RdfJsonWriter;
import javax.annotation.Nonnull;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.TreeMap;
import org.openrdf.model.Graph;
import org.openrdf.model.Statement;
import org.openrdf.rio.RDFHandlerException;
import org.openrdf.rio.RDFWriter;
import org.openrdf.rio.n3.N3Writer;
import org.openrdf.rio.rdfxml.util.RDFXMLPrettyWriter;
/***********************************************************************************************************************
*
* @author Fabrizio Giudici
* @version $Id$
*
**********************************************************************************************************************/
public class DefaultGraphSerializer implements GraphSerializer
{
private final Map uriMapByPrefix = new TreeMap();
private final StatementComparator statementComparator = new StatementComparator();
/*******************************************************************************************************************
*
* {@inheritDoc}
*
******************************************************************************************************************/
public void write (final @Nonnull Graph graph, @Nonnull OutputStream os, final @Nonnull String mimeType)
throws IOException, RDFHandlerException
{
if (GraphSerializer.MIME_RDF_JSON.equals(mimeType))
{
os = new JsonPrettyPrinterStream(os);
}
write(graph, new OutputStreamWriter(os, "UTF-8"), mimeType);
}
/*******************************************************************************************************************
*
* {@inheritDoc}
*
******************************************************************************************************************/
public void write (final @Nonnull Graph graph, final @Nonnull Writer w, final @Nonnull String mimeType)
throws IOException, RDFHandlerException
{
RDFWriter rdfWriter = null;
// We're not using yet the registry since we don't know whether it works with Android
if (GraphSerializer.MIME_RDF_JSON.equals(mimeType))
{
rdfWriter = new RdfJsonWriter(w);
}
else if(GraphSerializer.MIME_RDF_XML.equals(mimeType))
{
rdfWriter = new RDFXMLPrettyWriter(w);
}
else if(GraphSerializer.MIME_N3.equals(mimeType))
{
rdfWriter = new N3Writer(w);
}
else
{
throw new RDFHandlerException("No writer for MIME type: " + mimeType);
}
for (final Entry e : uriMapByPrefix.entrySet())
{
rdfWriter.handleNamespace(e.getKey(), e.getValue());
}
write(graph, rdfWriter);
w.flush(); // some writers (e.g. json) seems to need it
}
/*******************************************************************************************************************
*
* {@inheritDoc}
*
******************************************************************************************************************/
public void handleNamespace (final @Nonnull String prefix, final @Nonnull String uri)
{
uriMapByPrefix.put(prefix, uri);
}
/*******************************************************************************************************************
*
* {@inheritDoc}
*
******************************************************************************************************************/
private void write (final @Nonnull Graph graph, final @Nonnull RDFWriter writer)
throws RDFHandlerException
{
writer.startRDF();
for (final Statement statement : sortedAndUnique(graph))
{
writer.handleStatement(statement);
}
writer.endRDF();
}
/*******************************************************************************************************************
*
*
******************************************************************************************************************/
@Nonnull
private List sortedAndUnique (final @Nonnull Collection statements)
{
final List result = new ArrayList(statements);
if (!result.isEmpty())
{
Collections.sort(result, statementComparator);
final Iterator i = result.iterator();
Statement previous = i.next();
while (i.hasNext())
{
final Statement statement = i.next();
if (statementComparator.compare(statement, previous) == 0)
{
i.remove();
}
previous = statement;
}
}
return result;
}
}