/**
* Copyright 2005-2014 Restlet
*
* The contents of this file are subject to the terms of one of the following
* open source licenses: Apache 2.0 or or EPL 1.0 (the "Licenses"). You can
* select the license that you prefer but you may not use this file except in
* compliance with one of these Licenses.
*
* You can obtain a copy of the Apache 2.0 license at
* http://www.opensource.org/licenses/apache-2.0
*
* You can obtain a copy of the EPL 1.0 license at
* http://www.opensource.org/licenses/eclipse-1.0
*
* See the Licenses for the specific language governing permissions and
* limitations under the Licenses.
*
* Alternatively, you can obtain a royalty free commercial license with less
* limitations, transferable or non-transferable, directly at
* http://restlet.com/products/restlet-framework
*
* Restlet is a registered trademark of Restlet S.A.S.
*/
package org.restlet.ext.rdf.internal.n3;
import java.io.IOException;
import java.io.Writer;
import java.util.Map;
import org.restlet.data.Reference;
import org.restlet.ext.rdf.Graph;
import org.restlet.ext.rdf.GraphHandler;
import org.restlet.ext.rdf.Link;
import org.restlet.ext.rdf.Literal;
import org.restlet.ext.rdf.internal.RdfConstants;
import org.restlet.ext.rdf.internal.turtle.Context;
/**
* Handler of RDF content according to the N3 notation.
*
* @author Thierry Boileau
*/
public class RdfN3Writer extends GraphHandler {
/** The current context object. */
private Context context;
/** The preceding predicate used for factorization matter. */
private Reference precPredicate;
/** The preceding source used for factorization matter. */
private Reference precSource;
/** The character writer. */
private Writer writer;
/** Indicates if the end of the statement is to be written. */
private boolean writingExtraDot;
/**
* Constructor.
*
* @param writer
* The character writer to write to.
* @throws IOException
*/
public RdfN3Writer(Writer writer) throws IOException {
super();
this.context = new Context();
this.writer = writer;
Map<String, String> prefixes = context.getPrefixes();
prefixes.put(RdfConstants.RDF_SCHEMA.toString(), "rdf");
prefixes.put(RdfConstants.RDF_SYNTAX.toString(), "rdfs");
prefixes.put("http://www.w3.org/2000/10/swap/grammar/bnf#", "cfg");
prefixes.put("http://www.w3.org/2000/10/swap/grammar/n3#", "n3");
prefixes.put("http://www.w3.org/2000/10/swap/list#", "list");
prefixes.put("http://www.w3.org/2000/10/swap/pim/doc#", "doc");
prefixes.put("http://www.w3.org/2002/07/owl#", "owl");
prefixes.put("http://www.w3.org/2000/10/swap/log#", "log");
prefixes.put("http://purl.org/dc/elements/1.1/", "dc");
prefixes.put("http://www.w3.org/2001/XMLSchema#", "type");
for (String key : prefixes.keySet()) {
this.writer.append("@prefix ").append(prefixes.get(key))
.append(": <").append(key).append(">.\n");
}
this.writer.append("@keywords a, is, of, has.\n");
}
@Override
public void endGraph() throws IOException {
this.writer.write(".\n");
this.writer.flush();
}
@Override
public void link(Graph source, Reference typeRef, Literal target) {
try {
this.writer.write("{");
write(source);
this.writer.write("} ");
write(typeRef, this.context.getPrefixes());
this.writer.write(" ");
write(target);
this.precSource = null;
this.precPredicate = typeRef;
this.writingExtraDot = true;
} catch (IOException e) {
org.restlet.Context.getCurrentLogger().warning(
"Cannot write the representation of a statement due to "
+ e.getMessage());
}
}
@Override
public void link(Graph source, Reference typeRef, Reference target) {
try {
this.writer.write("{");
write(source);
this.writer.write("} ");
write(typeRef, this.context.getPrefixes());
this.writer.write(" ");
write(target, this.context.getPrefixes());
this.precSource = null;
this.precPredicate = typeRef;
this.writingExtraDot = true;
} catch (IOException e) {
org.restlet.Context.getCurrentLogger().warning(
"Cannot write the representation of a statement due to "
+ e.getMessage());
}
}
@Override
public void link(Reference source, Reference typeRef, Literal target) {
try {
if (source.equals(this.precSource)) {
if (typeRef.equals(this.precPredicate)) {
this.writer.write(", ");
} else {
this.writer.write("; ");
write(typeRef, this.context.getPrefixes());
this.writer.write(" ");
}
} else {
if (this.writingExtraDot) {
this.writer.write(".\n");
}
write(source, this.context.getPrefixes());
this.writer.write(" ");
write(typeRef, this.context.getPrefixes());
this.writer.write(" ");
}
write(target);
this.precSource = source;
this.precPredicate = typeRef;
this.writingExtraDot = true;
} catch (IOException e) {
org.restlet.Context.getCurrentLogger().warning(
"Cannot write the representation of a statement due to "
+ e.getMessage());
}
}
@Override
public void link(Reference source, Reference typeRef, Reference target) {
try {
if (source.equals(this.precSource)) {
if (typeRef.equals(this.precPredicate)) {
this.writer.write(", ");
} else {
this.writer.write("; ");
write(typeRef, this.context.getPrefixes());
this.writer.write(" ");
}
} else {
if (this.writingExtraDot) {
this.writer.write(".\n");
}
write(source, this.context.getPrefixes());
this.writer.write(" ");
write(typeRef, this.context.getPrefixes());
this.writer.write(" ");
}
write(target, this.context.getPrefixes());
this.precSource = source;
this.precPredicate = typeRef;
this.writingExtraDot = true;
} catch (IOException e) {
org.restlet.Context.getCurrentLogger().warning(
"Cannot write the representation of a statement due to "
+ e.getMessage());
}
}
/**
* Write the representation of the given graph of links.
*
* @param linkset
* the given graph of links.
* @throws IOException
*/
private void write(Graph linkset) throws IOException {
for (Link link : linkset) {
if (link.hasReferenceSource()) {
if (link.hasReferenceTarget()) {
link(link.getSourceAsReference(), link.getTypeRef(),
link.getTargetAsReference());
} else if (link.hasLiteralTarget()) {
link(link.getSourceAsReference(), link.getTypeRef(),
link.getTargetAsLiteral());
} else if (link.hasLinkTarget()) {
// TODO Hande source as link.
} else {
org.restlet.Context
.getCurrentLogger()
.warning(
"Cannot write the representation of a statement due to the fact that the object is neither a Reference nor a literal.");
}
} else if (link.hasGraphSource()) {
this.writingExtraDot = false;
if (link.hasReferenceTarget()) {
link(link.getSourceAsGraph(), link.getTypeRef(),
link.getTargetAsReference());
} else if (link.hasLiteralTarget()) {
link(link.getSourceAsGraph(), link.getTypeRef(),
link.getTargetAsLiteral());
} else if (link.hasLinkTarget()) {
// TODO Handle source as link.
} else {
org.restlet.Context
.getCurrentLogger()
.warning(
"Cannot write the representation of a statement due to the fact that the object is neither a Reference nor a literal.");
}
this.writer.write(".\n");
}
this.precSource = link.getSourceAsReference();
this.precPredicate = link.getTypeRef();
}
}
/**
* Writes the representation of a literal.
*
* @param literal
* The literal to write.
* @throws IOException
*/
private void write(Literal literal) throws IOException {
// Write it as a string
this.writer.write("\"");
if (literal.getValue().contains("\n")) {
this.writer.write("\"");
this.writer.write("\"");
this.writer.write(literal.getValue());
this.writer.write("\"");
this.writer.write("\"");
} else {
this.writer.write(literal.getValue());
}
this.writer.write("\"");
if (literal.getDatatypeRef() != null) {
this.writer.write("^^");
write(literal.getDatatypeRef(), context.getPrefixes());
}
if (literal.getLanguage() != null) {
this.writer.write("@");
this.writer.write(literal.getLanguage().toString());
}
}
/**
* Writes the representation of a given reference.
*
* @param reference
* The reference to write.
* @param prefixes
* The map of known namespaces.
* @throws IOException
*/
private void write(Reference reference, Map<String, String> prefixes)
throws IOException {
String uri = reference.toString();
if (Link.isBlankRef(reference)) {
this.writer.write(uri);
} else {
boolean found = false;
for (String key : prefixes.keySet()) {
if (uri.startsWith(key)) {
found = true;
this.writer.append(prefixes.get(key));
this.writer.append(":");
this.writer.append(uri.substring(key.length()));
break;
}
}
if (!found) {
this.writer.append("<");
this.writer.append(uri);
this.writer.append(">");
}
}
}
}