org.deri.xquery.saxon.EvaluatorExternalFunctions Maven / Gradle / Ivy
/**
*
* Copyright (C) 2011, NUI Galway.
* All rights reserved.
*
* The software in this package is published under the terms of the BSD style license a copy of which has been included
* with this distribution in the bsb_license.txt file and/or available on NUI Galway Server at
* http://xsparql.deri.ie/license/bsd_license.txt
*
* Created: 09 February 2011, Reasoning and Querying Unit (URQ), Digital Enterprise Research Institute (DERI) on behalf of
* NUI Galway.
*/
/**
*
*/
package org.deri.xquery.saxon;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import net.sf.json.JSON;
import net.sf.json.JSONSerializer;
import net.sf.json.xml.XMLSerializer;
import org.deri.xquery.DatasetResults;
import com.hp.hpl.jena.query.Dataset;
import com.hp.hpl.jena.query.DatasetFactory;
import com.hp.hpl.jena.query.Query;
import com.hp.hpl.jena.query.QueryExecution;
import com.hp.hpl.jena.query.QueryExecutionFactory;
import com.hp.hpl.jena.query.QueryFactory;
import com.hp.hpl.jena.query.QuerySolution;
import com.hp.hpl.jena.query.QuerySolutionMap;
import com.hp.hpl.jena.query.ResultSet;
import com.hp.hpl.jena.query.ResultSetRewindable;
import com.hp.hpl.jena.tdb.TDBFactory;
/**
* Library of Java methods for usage from within XQuery queries when using Saxon
*
* @author Stefan Bischof
* @author Nuno Lopes
*
*/
class EvaluatorExternalFunctions {
private static Map scopedDataset = new HashMap();
private static String TDBLocation = System.getProperty("user.home") + "/.xsparql/TDB";
// ----------------------------------------------------------------------------------------------------
// constructed Dataset
/**
* Saves string s to a local file.
*
* @param prefix
* Turtle preamble
* @param n3
* Turtle content
* @return URI of local file containing string s
*/
public static String turtleGraphToURI(String prefix, String n3) {
String ret = "";
try {
// Create temp file.
File temp = File.createTempFile("sparqlGraph", ".n3");
// Delete temp file when program exits.
temp.deleteOnExit();
// Write to temp file
BufferedWriter out = new BufferedWriter(new FileWriter(temp));
out.write(prefix);
out.write(n3.replace("\\", "\\\\")); // re-escape any blackslashes
out.close();
ret = "file://" + temp.getAbsolutePath();
} catch (IOException e) {
}
return ret;
}
public static Dataset getTDBDataset(String location) {
// check if the directory exists and if not create it
if (!new File(location).exists()) {
try {
new File(location).mkdirs();
} catch (Exception e) {
System.err.println("Error retrieving the datasets: " + e.getMessage());
System.exit(1);
}
}
Dataset dataset = TDBFactory.createDataset(location);
return dataset;
}
public static Dataset getTDBDataset() {
String location = TDBLocation;
return getTDBDataset(location);
}
public static String getDefaultTDBDatasetLocation() {
return TDBLocation;
}
// ----------------------------------------------------------------------------------------------------
// Scoped Dataset
/**
* Evaluates a SPARQL query, storing the bindings to be reused later. Used for
* the ScopedDataset.
*
* @param q
* query to be executed
* @param id
* solution id
* @return XML results of the query
*/
public static ResultSet createScopedDataset(String q, String id) {
// System.out.println("createScopedDataset(" + q + "," + id + ")");
if (scopedDataset.containsKey(id)) {
// error?
}
Query query = QueryFactory.create(q);
Dataset dataset = DatasetFactory.create(query.getGraphURIs(),
query.getNamedGraphURIs());
QueryExecution qe = QueryExecutionFactory.create(query, dataset);
ResultSet resultSet = qe.execSelect();
DatasetResults ds = new DatasetResults(dataset);
ResultSetRewindable results = ds.addResults(resultSet);
scopedDataset.put(id, ds);
return results;
}
/**
* Evaluates a SPARQL query, using previously stored dataset and bindings.
* Used for the ScopedDataset.
*
* @param q
* query to be executed
* @param id
* solution id
* @param joinVars
* joining variables that will be put in the initialBinding
* @param pos
* current iteration
* @return XML results of the query
*/
public static ResultSet sparqlScopedDataset(String q, String id,
String joinVars, int pos) {
// System.out.println("sparqlScopedDataset(" + q + "," + id + "," +joinVars+
// "," +pos+ ")");
if (!scopedDataset.containsKey(id)) {
// error ??
}
Dataset dataset = scopedDataset.get(id).getDataset();
ResultSetRewindable results = scopedDataset.get(id).getResults();
results.reset();
// used to filter solutions
QuerySolutionMap initialBinding = createSolutionMap(results, joinVars, pos);
QueryExecution qe = QueryExecutionFactory
.create(q, dataset, initialBinding);
ResultSet resultSet = qe.execSelect();
// store current resultSet in case there is further nesting
ResultSetRewindable results2 = scopedDataset.get(id).addResults(resultSet);
return results2;
}
/**
* Creates an initialBinding from the previous solutions and the join vars.
*
* @param results
* previous resultSet
* @param joinVars
* joining variables that will be put in the initialBinding
* @param pos
* current iteration
* @return QuerySolutionMap to be used for filtering results
*/
private static QuerySolutionMap createSolutionMap(
ResultSetRewindable results, String joinVars, int pos) {
QuerySolutionMap initialBinding = new QuerySolutionMap();
String[] joinVarsArray = joinVars.split(",");
QuerySolution s = new QuerySolutionMap();
// move to current position of results
int it = 1;
while (results.hasNext()) {
QuerySolution qs = results.next();
if (it == pos) {
s = qs;
break;
}
it++;
}
Iterator iterator = Arrays.asList(joinVarsArray).iterator();
while (iterator.hasNext()) {
String st = iterator.next();
if (s.contains(st)) {
initialBinding.add(st, s.get(st));
}
}
return initialBinding;
}
/**
* Deletes stored dataset and solutions.
*
* @param id
* solution id
*/
public static void deleteScopedDataset(String id) {
// System.out.println("deleteScopedDataset(" + id + ")");
// delete dataset from scope, no longer needed
scopedDataset.remove(id);
}
/**
* Deletes the last results from the stack.
*
* @param id
* solution id
*/
public static void scopedDatasetPopResults(String id) {
// System.out.println("scopedDatasetPopResults(" + id + ")");
// delete dataset from scope, no longer needed
if (scopedDataset.size() > 0) {
scopedDataset.get(id).popResults();
}
}
/**
* Retrieves data from a url, Converts JSON data to XML
*
* @param URL location of the data
*
*/
public static String jsonToXML(String loc) {
String xml = "";
String jsonData = "";
try {
// Send data
URL url = new URL(loc);
BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));
String inputLine;
while ((inputLine = in.readLine()) != null) {
jsonData+=inputLine;
}
// String jsonData = IOUtils.toString(is);
XMLSerializer serializer = new XMLSerializer();
JSON json = JSONSerializer.toJSON( jsonData );
serializer.setTypeHintsEnabled(false);
xml = serializer.write( json );
in.close();
} catch (Exception e) {
e.printStackTrace();
System.exit(1);
}
return xml;
}
}
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