/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.
*/
package org.apache.jena.n3;
//import org.apache.commons.logging.*;
import java.util.* ;
import org.apache.jena.rdf.model.* ;
import org.apache.jena.shared.JenaException ;
import org.apache.jena.util.iterator.* ;
import org.apache.jena.vocabulary.RDF ;
import org.apache.jena.vocabulary.RDFS ;
/** An N3 pretty printer.
* Tries to make N3 data look readable - works better on regular data.
*/
public class N3JenaWriterPP extends N3JenaWriterCommon
/*implements RDFWriter*/
{
// This N3 writer proceeds in 2 stages. First, it analysises the model to be
// written to extract information that is going to be specially formatted
// (RDF lists, small anon nodes) and to calculate the prefixes that will be used.
final protected boolean doObjectListsAsLists = getBooleanValue("objectLists", true) ;
// Data structures used in controlling the formatting
protected Set<Resource> rdfLists = null ; // Heads of lists
protected Set<Resource> rdfListsAll = null ; // Any resources in a collection
protected Set<Resource> rdfListsDone = null ; // RDF lists written
protected Set<RDFNode> oneRefObjects = null ; // Bnodes referred to once as an object - can inline
protected Set<Resource> oneRefDone = null ; // Things done - so we can check for missed items
// Do we do nested (one reference) nodes?
protected boolean allowDeep = true ;
static final protected String objectListSep = " , " ;
// ----------------------------------------------------
// Prepatation stage
@Override
protected void prepare(Model model)
{
prepareLists(model) ;
prepareOneRefBNodes(model) ;
}
// Find well-formed RDF lists - does not find empty lists (this is intentional)
// Works by finding all tails, and work backwards to the head.
// RDF lists may, or may not, have a type element.
// Should do this during preparation, not as objects found during the write
// phase.
protected void prepareLists(Model model)
{
Set<Resource> thisListAll = new HashSet<>();
StmtIterator listTailsIter = model.listStatements(null, RDF.rest, RDF.nil);
// For every tail of a list
//tailLoop:
for ( ; listTailsIter.hasNext() ; )
{
// The resource for the current element being considered.
Resource listElement = listTailsIter.nextStatement().getSubject() ;
// The resource pointing to the link we have just looked at.
Resource validListHead = null ;
// Chase to head of list
for ( ; ; )
{
boolean isOK = checkListElement(listElement) ;
if ( ! isOK )
break ;
// At this point the element is exactly a collection element.
if ( N3JenaWriter.DEBUG ) out.println("# RDF list all: "+formatResource(listElement)) ;
validListHead = listElement ;
thisListAll.add(listElement) ;
// Find the previous node.
StmtIterator sPrev = model.listStatements(null, RDF.rest, listElement) ;
if ( ! sPrev.hasNext() )
// No rdf:rest link
break ;
// Valid pretty-able list. Might be longer.
listElement = sPrev.nextStatement().getSubject() ;
if ( sPrev.hasNext() )
{
if ( N3JenaWriter.DEBUG ) out.println("# RDF shared tail from "+formatResource(listElement)) ;
break ;
}
}
// At head of a pretty-able list - add its elements and its head.
if ( N3JenaWriter.DEBUG ) out.println("# Collection list head: "+formatResource(validListHead)) ;
rdfListsAll.addAll(thisListAll) ;
if ( validListHead != null )
rdfLists.add(validListHead) ;
}
listTailsIter.close() ;
}
// Validate one list element.
protected boolean checkListElement(Resource listElement)
{
// Must be a blank node for abbreviated form.
if ( ! listElement.isAnon() )
return false ;
if (!listElement.hasProperty(RDF.rest)
|| !listElement.hasProperty(RDF.first))
{
if (N3JenaWriter.DEBUG)
out.println(
"# RDF list element does not have required properties: "
+ formatResource(listElement));
return false;
}
// Must be exactly two properties (the ones we just tested for)
// or three including the RDF.type RDF.List statement.
int numProp = countProperties(listElement);
if ( numProp == 2)
// Must have exactly the properties we just tested for.
return true ;
// rdf:type is not implicit.
// if (numProp == 3)
// {
// if (listElement.hasProperty(RDF.type, RDF.List))
// return true;
// if (N3JenaWriter.DEBUG)
// out.println(
// "# RDF list element: 3 properties but no rdf:type rdf:List"
// + formatResource(listElement));
// return false;
// }
if (N3JenaWriter.DEBUG)
out.println(
"# RDF list element does not right number of properties: "
+ formatResource(listElement));
return false;
}
// Find bnodes that are objects of only one statement (and hence can be inlined)
// which are not RDF lists.
// Could do this testing at write time (unlike lists)
protected void prepareOneRefBNodes(Model model)
{
NodeIterator objIter = model.listObjects() ;
for ( ; objIter.hasNext() ; )
{
RDFNode n = objIter.nextNode() ;
if ( testOneRefBNode(n) )
oneRefObjects.add(n) ;
objIter.close() ;
// N3JenaWriter.DEBUG
if ( N3JenaWriter.DEBUG )
{
out.println("# RDF Lists = "+rdfLists.size()) ;
out.println("# RDF ListsAll = "+rdfListsAll.size()) ;
out.println("# oneRefObjects = "+oneRefObjects.size()) ;
}
}
}
protected boolean testOneRefBNode(RDFNode n)
{
if ( ! ( n instanceof Resource ) )
return false ;
Resource obj = (Resource)n ;
if ( ! obj.isAnon() )
return false ;
// In a list - done as list, not as embedded bNode.
if ( rdfListsAll.contains(obj) )
// RDF list (head or element)
return false ;
StmtIterator pointsToIter = obj.getModel().listStatements(null, null, obj) ;
if ( ! pointsToIter.hasNext() )
// Corrupt graph!
throw new JenaException("N3: found object with no arcs!") ;
pointsToIter.nextStatement() ;
if ( pointsToIter.hasNext() )
return false ;
if ( N3JenaWriter.DEBUG )
out.println("# OneRef: "+formatResource(obj)) ;
return true ;
}
// ----------------------------------------------------
// Output stage
// Property order is:
// 1 - rdf:type (as "a")
// 2 - other rdf: rdfs: namespace items (sorted)
// 3 - all other properties, sorted by URI (not qname)
@Override
protected ClosableIterator<Property> preparePropertiesForSubject(Resource r)
{
Set<Property> seen = new HashSet<>() ;
boolean hasTypes = false ;
SortedMap<String, Property> tmp1 = new TreeMap<>() ;
SortedMap<String, Property> tmp2 = new TreeMap<>() ;
StmtIterator sIter = r.listProperties();
for ( ; sIter.hasNext() ; )
{
Property p = sIter.nextStatement().getPredicate() ;
if ( seen.contains(p) )
continue ;
seen.add(p) ;
if ( p.equals(RDF.type) )
{
hasTypes = true ;
continue ;
}
if ( p.getURI().startsWith(RDF.getURI()) ||
p.getURI().startsWith(RDFS.getURI()) )
{
tmp1.put(p.getURI(), p) ;
continue ;
}
tmp2.put(p.getURI(), p) ;
}
sIter.close() ;
ExtendedIterator<Property> eIter = null ;
if ( hasTypes )
eIter = new SingletonIterator<>(RDF.type) ;
ExtendedIterator<Property> eIter2 = WrappedIterator.create(tmp1.values().iterator()) ;
eIter = (eIter == null) ? eIter2 : eIter.andThen(eIter2) ;
eIter2 = WrappedIterator.create(tmp2.values().iterator()) ;
eIter = (eIter == null) ? eIter2 : eIter.andThen(eIter2) ;
return eIter ;
}
@Override
protected boolean skipThisSubject(Resource subj)
{
return rdfListsAll.contains(subj) ||
oneRefObjects.contains(subj) ;
}
// protected void writeModel(Model model)
// {
// super.writeModel(model) ;
//
//
// Before ...
@Override
protected void startWriting()
{
allocateDatastructures() ;
}
// Flush any unwritten objects.
// 1 - OneRef objects
// Normally there are "one ref" objects left
// However loops of "one ref" are possible.
// 2 - Lists
@Override
protected void finishWriting()
{
// Are there any unattached RDF lists?
// e..g ([] [] []) . in the data.
// We missed these earlier.
for ( Resource r : rdfLists )
{
if ( rdfListsDone.contains( r ) )
{
continue;
}
out.println();
if ( N3JenaWriter.DEBUG )
{
out.println( "# RDF List" );
}
// Includes the case of shared lists-as-objects.
// if (!r.isAnon() || countArcsTo(r) > 0 )
// {
// // Name it.
// out.print(formatResource(r));
// out.print(" :- ");
// }
// writeList(r);
// out.println(" .");
// Turtle does not have :-
writeListUnpretty( r );
}
// Finally, panic.
// Dump anything that has not been output yet.
oneRefObjects.removeAll(oneRefDone);
for ( RDFNode oneRefObject : oneRefObjects )
{
out.println();
if ( N3JenaWriter.DEBUG )
{
out.println( "# One ref" );
}
// Don't allow further one ref objects to be inlined.
allowDeep = false;
writeOneGraphNode( (Resource) oneRefObject );
allowDeep = true;
}
//out.println() ;
//writeModelSimple(model, bNodesMap, base) ;
out.flush();
clearDatastructures() ;
}
// Need to decide between one line or many.
// Very hard to do a pretty thing here because the objects may be large or small or a mix.
@Override
protected void writeObjectList(Resource subject, Property property)
{
// if ( ! doObjectListsAsLists )
// {
// super.writeObjectList(resource, property) ;
// return ;
// }
String propStr = formatProperty(property);
// Find which objects are simple (i.e. not nested structures)
StmtIterator sIter = subject.listProperties(property);
Set<RDFNode> simple = new HashSet<>() ;
Set<RDFNode> complex = new HashSet<>() ;
for (; sIter.hasNext();)
{
Statement stmt = sIter.nextStatement();
RDFNode obj = stmt.getObject() ;
if ( isSimpleObject(obj) )
simple.add(obj) ;
else
complex.add(obj) ;
}
sIter.close() ;
// Write property/simple objects
if ( simple.size() > 0 )
{
String padSp = null ;
// Simple objects - allow property to be long and alignment to be lost
if ((propStr.length()+minGap) <= widePropertyLen)
padSp = pad(calcPropertyPadding(propStr)) ;
if ( doObjectListsAsLists )
{
// Write all simple objects as one list.
out.print(propStr);
out.incIndent(indentObject) ;
if ( padSp != null )
out.print(padSp) ;
else
out.println() ;
for (Iterator<RDFNode> iter = simple.iterator(); iter.hasNext();)
{
RDFNode n = iter.next();
writeObject(n);
// As an object list
if (iter.hasNext())
out.print(objectListSep);
}
out.decIndent(indentObject) ;
}
else
{
for (Iterator<RDFNode> iter = simple.iterator(); iter.hasNext();)
{
// This is also the same as the complex case
// except the width the property can go in is different.
out.print(propStr);
out.incIndent(indentObject) ;
if ( padSp != null )
out.print(padSp) ;
else
out.println() ;
RDFNode n = iter.next();
writeObject(n);
out.decIndent(indentObject) ;
// As an object list
if (iter.hasNext())
out.println(" ;");
}
}
}
// Now do complex objects.
// Write property each time for a complex object.
// Do not allow over long properties but same line objects.
if (complex.size() > 0)
{
// Finish the simple list if there was one
if ( simple.size() > 0 )
out.println(" ;");
int padding = -1 ;
String padSp = null ;
// Can we fit teh start of teh complex object on this line?
// Complex objects - do not allow property to be long and alignment to be lost
if ((propStr.length()+minGap) <= propertyCol)
{
padding = calcPropertyPadding(propStr) ;
padSp = pad(padding) ;
}
for (Iterator<RDFNode> iter = complex.iterator(); iter.hasNext();)
{
int thisIndent = indentObject ;
//if ( i )
out.incIndent(thisIndent);
out.print(propStr);
if ( padSp != null )
out.print(padSp) ;
else
out.println() ;
RDFNode n = iter.next();
writeObject(n);
out.decIndent(thisIndent);
if ( iter.hasNext() )
out.println(" ;");
}
}
return;
}
protected boolean isSimpleObject(RDFNode node)
{
if (node instanceof Literal)
return true ;
Resource rObj = (Resource) node;
if ( allowDeep && oneRefObjects.contains(rObj) )
return false ;
return true ;
}
@Override
protected void writeObject(RDFNode node)
{
if (node instanceof Literal)
{
writeLiteral((Literal) node);
return;
}
Resource rObj = (Resource) node;
if ( allowDeep && ! isSimpleObject(rObj))
{
oneRefDone.add(rObj);
ClosableIterator<Property> iter = preparePropertiesForSubject(rObj);
if (! iter.hasNext() )
{
// No properties.
out.print("[]");
}
else
{
out.print("[ ");
out.incIndent(2);
writePropertiesForSubject(rObj, iter);
out.decIndent(2);
out.println() ;
// Line up []
out.print("]");
}
iter.close();
return ;
}
if (rdfLists.contains(rObj))
if (countArcsTo(rObj) <= 1)
{
writeList(rObj);
return;
}
out.print(formatResource(rObj));
}
// Need to out.print in short (all on one line) and long forms (multiple lines)
protected void writeList(Resource resource)
{
out.print( "(");
out.incIndent(2) ;
boolean listFirst = true;
for (Iterator<RDFNode> iter = rdfListIterator(resource); iter.hasNext();)
{
if (!listFirst)
out.print( " ");
listFirst = false;
RDFNode n = iter.next();
writeObject(n) ;
}
out.print( ")");
out.decIndent(2) ;
rdfListsDone.add(resource);
}
// Need to out.print in long (triples) form.
protected void writeListUnpretty(Resource r)
{
//for ( ; ! r.equals(RDF.nil); )
{
// Write statements at this node.
StmtIterator sIter = r.getModel().listStatements(r, null, (RDFNode)null) ;
for ( ; sIter.hasNext() ; )
{
Statement s = sIter.next() ;
writeStatement(s) ;
}
// Look for rdf:rest.
sIter = r.getModel().listStatements(r, RDF.rest, (RDFNode)null) ;
for ( ; sIter.hasNext() ; )
{
Statement s = sIter.next() ;
RDFNode nextNode = s.getObject() ;
if ( nextNode instanceof Resource )
{
Resource r2 = (Resource)nextNode ;
writeListUnpretty(r2) ;
}
else
writeStatement(s) ;
}
}
}
private void writeStatement(Statement s)
{
out.print(formatResource(s.getSubject()));
out.print(" ") ;
out.print(formatResource(s.getPredicate())) ;
out.print(" ") ;
out.print(formatNode(s.getObject())) ;
out.println(" .") ;
}
// Called before each writing run.
protected void allocateDatastructures()
{
rdfLists = new HashSet<>() ;
rdfListsAll = new HashSet<>() ;
rdfListsDone = new HashSet<>() ;
oneRefObjects = new HashSet<>() ;
oneRefDone = new HashSet<>() ;
}
// Especially release large intermediate memory objects
protected void clearDatastructures()
{
rdfLists = null ;
rdfListsAll = null ;
rdfListsDone = null ;
oneRefObjects = null ;
oneRefDone = null ;
}
}