| /* |
| * 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 tdb.examples; |
| |
| import org.apache.jena.atlas.iterator.Filter ; |
| import org.apache.jena.atlas.lib.Tuple ; |
| |
| import org.apache.jena.graph.NodeFactory ; |
| import org.apache.jena.query.* ; |
| import org.apache.jena.sparql.core.DatasetGraph ; |
| import org.apache.jena.sparql.core.Quad ; |
| import org.apache.jena.sparql.sse.SSE ; |
| import org.apache.jena.tdb.TDB ; |
| import org.apache.jena.tdb.TDBFactory ; |
| import org.apache.jena.tdb.store.NodeId ; |
| import org.apache.jena.tdb.sys.SystemTDB ; |
| import org.apache.jena.tdb.sys.TDBInternal ; |
| |
| /** Example of how to filter quads as they are accessed at the lowest level. |
| * Can be used to exclude data from specific graphs. |
| * This mechanism is not limited to graphs - it works for properties or anything |
| * where the visibility of otherwise is determined by the elements of the quad. |
| * See <a href="http://incubator.apache.org/jena/documentation/tdb/quadfilter.html">QuadFiltering</a> |
| * for further details. |
| */ |
| |
| public class ExQuadFilter |
| { |
| private static String graphToHide = "http://example/g2" ; |
| |
| public static void main(String ... args) |
| { |
| // This also works for default union graph .... |
| TDB.getContext().setTrue(TDB.symUnionDefaultGraph) ; |
| |
| Dataset ds = setup() ; |
| Filter<Tuple<NodeId>> filter = createFilter(ds) ; |
| example(ds, filter) ; |
| } |
| |
| /** Example setup - in-memory dataset with two graphs, one triple in each */ |
| private static Dataset setup() |
| { |
| Dataset ds = TDBFactory.createDataset() ; |
| DatasetGraph dsg = ds.asDatasetGraph() ; |
| Quad q1 = SSE.parseQuad("(<http://example/g1> <http://example/s> <http://example/p> <http://example/o1>)") ; |
| Quad q2 = SSE.parseQuad("(<http://example/g2> <http://example/s> <http://example/p> <http://example/o2>)") ; |
| dsg.add(q1) ; |
| dsg.add(q2) ; |
| return ds ; |
| } |
| |
| /** Create a filter to exclude the graph http://example/g2 */ |
| private static Filter<Tuple<NodeId>> createFilter(Dataset ds) |
| { |
| // Filtering operates at a very low level: |
| // Need to know the internal identifier for the graph name. |
| final NodeId target = TDBInternal.getNodeId(ds, NodeFactory.createURI(graphToHide)) ; |
| |
| System.out.println("Hide graph: "+graphToHide+" --> "+target) ; |
| |
| // Filter for accept/reject as quad as being visible. |
| // Return true for "accept", false for "reject" |
| Filter<Tuple<NodeId>> filter = new Filter<Tuple<NodeId>>() { |
| @Override |
| public boolean accept(Tuple<NodeId> item) |
| { |
| // Reverse the lookup as a demo |
| //Node n = TDBInternal.getNode(target) ; |
| //System.err.println(item) ; |
| if ( item.size() == 4 && item.get(0).equals(target) ) |
| { |
| //System.out.println("Reject: "+item) ; |
| return false ; |
| } |
| //System.out.println("Accept: "+item) ; |
| return true ; |
| } } ; |
| |
| return filter ; |
| } |
| |
| private static void example(Dataset ds, Filter<Tuple<NodeId>> filter) |
| { |
| String[] x = { |
| "SELECT * { GRAPH ?g { ?s ?p ?o } }", |
| "SELECT * { ?s ?p ?o }", |
| // This filter does not hide the graph itself, just the quads associated with the graph. |
| "SELECT * { GRAPH ?g {} }" |
| } ; |
| |
| for ( String qs : x ) |
| { |
| example(ds, qs, filter) ; |
| example(ds, qs, null) ; |
| } |
| |
| } |
| |
| private static void example(Dataset ds, String qs, Filter<Tuple<NodeId>> filter) |
| { |
| System.out.println() ; |
| Query query = QueryFactory.create(qs) ; |
| System.out.println(qs) ; |
| QueryExecution qExec = QueryExecutionFactory.create(query, ds) ; |
| // Install filter for this query only. |
| if ( filter != null ) |
| { |
| System.out.println("Install quad-level filter") ; |
| qExec.getContext().set(SystemTDB.symTupleFilter, filter) ; |
| } |
| else |
| System.out.println("No quad-level filter") ; |
| ResultSetFormatter.out(qExec.execSelect()) ; |
| qExec.close() ; |
| |
| } |
| |
| } |