| /* |
| * 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 arq.examples.propertyfunction; |
| |
| import java.util.ArrayList ; |
| import java.util.Collection ; |
| import java.util.List ; |
| |
| import org.apache.jena.graph.Graph ; |
| import org.apache.jena.graph.Node ; |
| import org.apache.jena.graph.NodeFactory ; |
| import org.apache.jena.graph.Triple ; |
| import org.apache.jena.sparql.core.Var ; |
| import org.apache.jena.sparql.engine.ExecutionContext ; |
| import org.apache.jena.sparql.engine.QueryIterator ; |
| import org.apache.jena.sparql.engine.binding.Binding ; |
| import org.apache.jena.sparql.engine.binding.BindingFactory ; |
| import org.apache.jena.sparql.engine.binding.BindingMap ; |
| import org.apache.jena.sparql.engine.iterator.QueryIterNullIterator ; |
| import org.apache.jena.sparql.engine.iterator.QueryIterPlainWrapper ; |
| import org.apache.jena.sparql.engine.iterator.QueryIterSingleton ; |
| import org.apache.jena.sparql.pfunction.PFuncSimple ; |
| import org.apache.jena.sparql.util.NodeUtils ; |
| import org.apache.jena.util.iterator.ExtendedIterator ; |
| |
| /** Example property function that creates the association between a URI and it's localname. |
| * See also splitIRI which is more general. This is just an example. |
| * |
| * If it is not a URI, then does not match. |
| * |
| * Use as: |
| * |
| * <pre> |
| * ?uri ext:localname ?localname |
| * </pre> |
| * |
| * Depending on whether the subject/object are bound when called: |
| * <ul> |
| * <li>subject bound, object unbound => assign the local name to variable in object slot</li> |
| * <li>subject bound, object bound => check the subject has the local name given by object</li> |
| * <li>subject unbound, object bound => find all URIs in the model (s, p or o) that have that local name</li> |
| * <li>subject unbound, object unbound => generate all localname for all URI resources in the model</li> |
| * </ul> |
| * The two searching forms (subject unbound) are expensive. |
| |
| * Anything not a URI (subject) or string (object) causes no match. |
| * */ |
| |
| public class localname extends PFuncSimple |
| { |
| |
| @Override |
| public QueryIterator execEvaluated(Binding binding, Node nodeURI, Node predicate, Node nodeLocalname, ExecutionContext execCxt) |
| { |
| if ( ! nodeURI.isVariable() ) |
| return execFixedSubject(nodeURI, nodeLocalname, binding, execCxt) ; |
| else |
| return execAllNodes(Var.alloc(nodeURI), nodeLocalname, binding, execCxt) ; |
| } |
| |
| // Subject is bound : still two cases: object bound (do a check) and object unbound (assign the local name) |
| private QueryIterator execFixedSubject(Node nodeURI, Node nodeLocalname, Binding binding, ExecutionContext execCxt) |
| { |
| if ( ! nodeURI.isURI() ) |
| // Subject bound but not a URI |
| return QueryIterNullIterator.create(execCxt) ; |
| |
| // Subject is bound and a URI - get the localname as a Node |
| Node localname = NodeFactory.createLiteral(nodeURI.getLocalName()) ; |
| |
| // Object - unbound variable or a value? |
| if ( ! nodeLocalname.isVariable() ) |
| { |
| // Object bound or a query constant. Is it the same as the calculated value? |
| if ( nodeLocalname.equals(localname) ) |
| // Same |
| return QueryIterSingleton.create(binding, execCxt) ; |
| // No - different - no match. |
| return QueryIterNullIterator.create(execCxt) ; |
| } |
| |
| // Object unbound variable - assign the localname to it. |
| return QueryIterSingleton.create(binding, Var.alloc(nodeLocalname), localname, execCxt) ; |
| } |
| |
| // Unbound subject - work hard. |
| // Still two cases: object bound (filter by localname) and object unbound (generate all localnames for all URIs) |
| // Warning - will scan the entire graph (there is no localname index) but this example code. |
| |
| private QueryIterator execAllNodes(Var subjVar, Node nodeLocalname, Binding input, ExecutionContext execCxt) |
| { |
| if ( ! nodeLocalname.isVariable() ) |
| { |
| if ( ! nodeLocalname.isLiteral() ) |
| // Not a variable, not a literal=> can't match |
| return QueryIterNullIterator.create(execCxt) ; |
| |
| if( ! NodeUtils.isSimpleString(nodeLocalname) ) |
| return QueryIterNullIterator.create(execCxt) ; |
| } |
| |
| //Set bindings = new HashSet() ; // Use a Set if you want unique results. |
| List<Binding> bindings = new ArrayList<>() ; // Use a list if you want counting results. |
| Graph graph = execCxt.getActiveGraph() ; |
| |
| ExtendedIterator<Triple>iter = graph.find(Node.ANY, Node.ANY, Node.ANY) ; |
| for ( ; iter.hasNext() ; ) |
| { |
| Triple t = iter.next() ; |
| slot(bindings, input, t.getSubject(), subjVar, nodeLocalname) ; |
| slot(bindings, input, t.getPredicate(), subjVar, nodeLocalname) ; |
| slot(bindings, input, t.getObject(), subjVar, nodeLocalname) ; |
| } |
| return new QueryIterPlainWrapper(bindings.iterator(), execCxt) ; |
| } |
| |
| private void slot(Collection<Binding> bindings, Binding input, Node node, Var subjVar, Node nodeLocalname) |
| { |
| if ( ! node.isURI() ) return ; |
| Node localname = NodeFactory.createLiteral(node.getLocalName()) ; |
| if ( nodeLocalname.isVariable() ) |
| { |
| // Object is an unbound variable. |
| BindingMap b = BindingFactory.create(input) ; |
| // Bind a pair for subject and object variables |
| b.add(Var.alloc(subjVar), node) ; |
| b.add(Var.alloc(nodeLocalname), localname) ; |
| bindings.add(b) ; |
| return ; |
| } |
| |
| // Object is a value / bound variable. |
| if ( ! nodeLocalname.sameValueAs(localname) ) |
| return ; |
| // Bind subject to this node. |
| Binding b = BindingFactory.binding(input, subjVar, node) ; |
| bindings.add(b) ; |
| } |
| |
| } |