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ARQ is a SPARQL 1.1 query engine for Apache Jena
/*
* 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.sparql.util;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Objects;
import java.util.Set;
import org.apache.jena.atlas.lib.ListUtils;
import org.apache.jena.atlas.lib.SetUtils;
import org.apache.jena.atlas.lib.StrUtils ;
import org.apache.jena.datatypes.RDFDatatype ;
import org.apache.jena.datatypes.xsd.XSDDatatype ;
import org.apache.jena.graph.Node ;
import org.apache.jena.graph.NodeFactory ;
import org.apache.jena.iri.IRI ;
import org.apache.jena.rdf.model.impl.Util ;
import org.apache.jena.sparql.ARQInternalErrorException ;
import org.apache.jena.sparql.expr.Expr ;
import org.apache.jena.sparql.expr.ExprEvalException ;
import org.apache.jena.sparql.expr.NodeValue ;
import org.apache.jena.sparql.expr.nodevalue.NodeFunctions ;
import org.apache.jena.util.iterator.ExtendedIterator ;
import org.apache.jena.util.iterator.MapFilter ;
import org.apache.jena.util.iterator.MapFilterIterator ;
import org.apache.jena.util.iterator.WrappedIterator ;
/** Node utilities */
public class NodeUtils
{
public interface EqualityTest {
default boolean equal(Node n1, Node n2) {
return Objects.equals(n1, n2) ;
}
}
/** IRI to Node */
public static Node asNode(IRI iri) {
return NodeFactory.createURI(iri.toString()) ;
}
/** IRI string to Node */
public static Node asNode(String iri) {
return NodeFactory.createURI(iri) ;
}
/** Return true if the node is a literal and has a language tag */
public static boolean hasLang(Node node) {
if ( !node.isLiteral() )
return false ;
String x = node.getLiteralLanguage() ;
if ( x == null )
return false ;
if ( x.equals("") )
return false ;
return true ;
}
/** Get lexical for of anything that looks like a string literal.
* Returns the string value of plain literal (simple literal
* or lang string) or XSD string.
*/
public static String stringLiteral(Node literal) {
if ( !literal.isLiteral() )
return null ;
RDFDatatype dType = literal.getLiteralDatatype() ;
String langTag = literal.getLiteralLanguage() ;
// Language?
if ( langTag != null && !langTag.equals("") )
return literal.getLiteralLexicalForm() ;
if ( dType == null || dType.equals(XSDDatatype.XSDstring) )
return literal.getLiteralLexicalForm() ;
return null ;
}
/** Convert IRI Nodes to strings. Skip other kinds of Node */
public static Iterator nodesToURIs(Iterator iter) {
MapFilter mapper = new MapFilter() {
@Override
public String accept(Node x) {
return x.getURI() ;
}
} ;
ExtendedIterator eIter = WrappedIterator.create(iter) ;
Iterator conv = new MapFilterIterator<>(mapper, eIter) ;
return conv ;
}
/** @deprecated Use {@link #convertToSetNodes} */
@Deprecated
public static Set convertToNodes(Collection namedGraphs) {
return convertToSetNodes(namedGraphs);
}
/** Convert a collection of strings to a set of {@link Node Nodes}. */
public static Set convertToSetNodes(Collection namedGraphs) {
Set nodes = SetUtils.toSet(
namedGraphs.stream().map(NodeFactory::createURI)
);
return nodes;
}
/** Convert a collection of strings to a set of {@link Node Nodes}. */
public static Set convertToSetNodes(String... namedGraphs) {
return convertToSetNodes(Arrays.asList(namedGraphs));
}
/** Convert strings to a List of {@link Node Nodes}. */
public static List convertToListNodes(String... namedGraphs) {
return convertToListNodes(Arrays.asList(namedGraphs));
}
/** Convert strings to a List of {@link Node Nodes}. */
public static List convertToListNodes(List namedGraphs) {
List nodes = ListUtils.toList(
namedGraphs.stream().map(NodeFactory::createURI)
);
return nodes;
}
/** Compare two Nodes, based on their RDF terms forms, not value */
public static int compareRDFTerms(Node node1, Node node2) {
if ( node1 == null ) {
if ( node2 == null )
return Expr.CMP_EQUAL ;
return Expr.CMP_LESS ;
}
if ( node2 == null )
return Expr.CMP_GREATER ;
// No nulls.
if ( node1.isLiteral() && node2.isLiteral() )
return compareLiteralsBySyntax(node1, node2) ;
// One or both not literals
// Variables < Blank nodes < URIs < Literals
if ( node1.isVariable() ) {
if ( node2.isVariable() ) {
return StrUtils.strCompare(node1.getName(), node2.getName()) ;
}
// Variables before anything else
return Expr.CMP_LESS ;
}
if ( node2.isVariable() ) {
// node1 not variable
return Expr.CMP_GREATER ;
}
if ( node1.isBlank() ) {
if ( node2.isBlank() ) {
String s1 = node1.getBlankNodeId().getLabelString() ;
String s2 = node2.getBlankNodeId().getLabelString() ;
return StrUtils.strCompare(s1, s2) ;
}
// bNodes before anything but variables
return Expr.CMP_LESS ;
}
if ( node2.isBlank() )
// node1 not blank.
return Expr.CMP_GREATER ;
// Not blanks. 2 URI or one URI and one literal
if ( node1.isURI() ) {
if ( node2.isURI() ) {
String s1 = node1.getURI() ;
String s2 = node2.getURI() ;
return StrUtils.strCompare(s1, s2) ;
}
return Expr.CMP_LESS ;
}
if ( node2.isURI() )
return Expr.CMP_GREATER ;
// No URIs, no blanks nodes by this point
// And a pair of literals was filterd out first.
// Should not happen.
throw new ARQInternalErrorException("Compare: " + node1 + " " + node2) ;
}
/** Compare literals by kind - not by value.
* Gives a deterministic, stable, arbitrary ordering between unrelated literals.
*
* Ordering:
*
* - By lexical form
* - For same lexical form:
*
* - RDF 1.0 : simple literal < literal by lang < literal with type
*
- RDF 1.1 : xsd:string < rdf:langString < other dataypes.
* This is the closest to SPARQL 1.1: treat xsd:string as a simple literal
* - Lang by sorting on language tag (first case insensitive then case sensitive)
*
- Datatypes by URI
*
*/
private static int compareLiteralsBySyntax(Node node1, Node node2) {
if ( node1 == null || !node1.isLiteral() || node2 == null || !node2.isLiteral() )
throw new ARQInternalErrorException("compareLiteralsBySyntax called with non-literal: (" + node1 + "," + node2 + ")") ;
if ( node1.equals(node2) )
return Expr.CMP_EQUAL ;
String lex1 = node1.getLiteralLexicalForm() ;
String lex2 = node2.getLiteralLexicalForm() ;
int x = StrUtils.strCompare(lex1, lex2) ;
if ( x != Expr.CMP_EQUAL )
return x ;
// Same lexical form. Not .equals()
if ( isSimpleString(node1) ) // node2 not a simple string because they
// would be .equals
return Expr.CMP_LESS ;
if ( isSimpleString(node2) )
return Expr.CMP_GREATER ;
// Neither simple string / xsd:string(RDF 1.1)
// Both language strings?
if ( isLangString(node1) && isLangString(node2) ) {
String lang1 = node1.getLiteralLanguage() ;
String lang2 = node2.getLiteralLanguage() ;
x = StrUtils.strCompareIgnoreCase(lang1, lang2) ;
if ( x != Expr.CMP_EQUAL )
return x ;
x = StrUtils.strCompare(lang1, lang2) ;
if ( x != Expr.CMP_EQUAL )
return x ;
throw new ARQInternalErrorException("compareLiteralsBySyntax: lexical form and languages tags identical on non.equals literals") ;
}
// One a language string?
if ( isLangString(node1) )
return Expr.CMP_LESS ;
if ( isLangString(node2) )
return Expr.CMP_GREATER ;
// Both have other datatypes. Neither simple nor language tagged.
String dt1 = node1.getLiteralDatatypeURI() ;
String dt2 = node2.getLiteralDatatypeURI() ;
// Two datatypes.
return StrUtils.strCompare(dt1, dt2) ;
}
/**
* A Node is a simple string if:
* (RDF 1.0) No datatype and no language tag
* (RDF 1.1) xsd:string
*/
public static boolean isSimpleString(Node n) { return Util.isSimpleString(n) ; }
/**
* A Node is a language string if it has a language tag.
* (RDF 1.0 and RDF 1.1)
*/
public static boolean isLangString(Node n) { return Util.isLangString(n) ; }
// This is term comparison.
public static EqualityTest sameTerm = new EqualityTest() {
@Override
public boolean equal(Node n1, Node n2)
{
return NodeFunctions.sameTerm(n1, n2) ;
}
} ;
// This is value comparison
public static EqualityTest sameValue = new EqualityTest() {
@Override
public boolean equal(Node n1, Node n2)
{
NodeValue nv1 = NodeValue.makeNode(n1) ;
NodeValue nv2 = NodeValue.makeNode(n2) ;
try {
return NodeValue.sameAs(nv1, nv2) ;
} catch(ExprEvalException ex)
{
// Incomparible as values - must be different for our purposes.
return false ;
}
}
} ;
}