Java tutorial
/* * Copyright 2015 The Apache Software Foundation. * * Licensed 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 com.zazuko.wikidata.municipalities; import java.io.BufferedInputStream; import java.io.ByteArrayInputStream; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.StringWriter; import java.net.URISyntaxException; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import org.apache.http.HttpEntity; import org.apache.http.NameValuePair; import org.apache.http.client.entity.UrlEncodedFormEntity; import org.apache.http.client.methods.CloseableHttpResponse; import org.apache.http.client.methods.HttpPost; import org.apache.http.impl.client.CloseableHttpClient; import org.apache.http.impl.client.HttpClients; import org.apache.http.message.BasicNameValuePair; import org.apache.http.util.EntityUtils; import javax.xml.parsers.*; import org.apache.clerezza.commons.rdf.BlankNode; import org.apache.clerezza.commons.rdf.IRI; import org.apache.clerezza.commons.rdf.Language; import org.apache.clerezza.commons.rdf.RDFTerm; import org.apache.clerezza.commons.rdf.impl.utils.AbstractLiteral; import org.apache.http.client.methods.HttpGet; import org.apache.http.client.utils.URIBuilder; import org.xml.sax.*; import org.xml.sax.helpers.*; /** * * @author developer */ public class SparqlClient { final String endpoint; boolean debug = false; public SparqlClient(final String endpoint) { this.endpoint = endpoint; } List<Map<String, RDFTerm>> queryResultSet(final String query) throws IOException, URISyntaxException { CloseableHttpClient httpclient = HttpClients.createDefault(); URIBuilder builder = new URIBuilder(endpoint); builder.addParameter("query", query); HttpGet httpGet = new HttpGet(builder.build()); /*List<NameValuePair> nvps = new ArrayList<NameValuePair>(); nvps.add(new BasicNameValuePair("query", query)); httpGet.setEntity(new UrlEncodedFormEntity(nvps));*/ CloseableHttpResponse response2 = httpclient.execute(httpGet); try { HttpEntity entity2 = response2.getEntity(); InputStream in = entity2.getContent(); if (debug) { ByteArrayOutputStream baos = new ByteArrayOutputStream(); for (int ch = in.read(); ch != -1; ch = in.read()) { System.out.print((char) ch); baos.write(ch); } in = new ByteArrayInputStream(baos.toByteArray()); } SAXParserFactory spf = SAXParserFactory.newInstance(); spf.setNamespaceAware(true); SAXParser saxParser = spf.newSAXParser(); XMLReader xmlReader = saxParser.getXMLReader(); final SparqlsResultsHandler sparqlsResultsHandler = new SparqlsResultsHandler(); xmlReader.setContentHandler(sparqlsResultsHandler); xmlReader.parse(new InputSource(in)); /* for (int ch = in.read(); ch != -1; ch = in.read()) { System.out.print((char)ch); } */ // do something useful with the response body // and ensure it is fully consumed EntityUtils.consume(entity2); return sparqlsResultsHandler.getResults(); } catch (ParserConfigurationException ex) { throw new RuntimeException(ex); } catch (SAXException ex) { throw new RuntimeException(ex); } finally { response2.close(); } } final public static class SparqlsResultsHandler extends DefaultHandler { private String currentBindingName; private Map<String, RDFTerm> currentResult = null; private final List<Map<String, RDFTerm>> results = new ArrayList<>(); private boolean readingValue; private String lang; //the xml:lang attribute of a literal private StringWriter valueWriter; private Map<String, BlankNode> bNodeMap = new HashMap<>(); private static final IRI XSD_STRING = new IRI("http://www.w3.org/2001/XMLSchema#string"); private static final IRI RDF_LANG_STRING = new IRI("http://www.w3.org/1999/02/22-rdf-syntax-ns#langString"); private RDFTerm getBNode(String value) { if (!bNodeMap.containsKey(value)) { bNodeMap.put(value, new BlankNode()); } return bNodeMap.get(value); } private List<Map<String, RDFTerm>> getResults() { return results; } enum BindingType { uri, bnode, literal; } @Override public void startDocument() throws SAXException { } @Override public void startElement(String namespaceURI, String localName, String qName, Attributes atts) throws SAXException { if ("http://www.w3.org/2005/sparql-results#".equals(namespaceURI)) { if ("result".equals(localName)) { if (currentResult != null) { throw new SAXException("unexpected tag <result>"); } currentResult = new HashMap<>(); } else if ("binding".equals(localName)) { if (currentResult == null) { throw new SAXException("unexpected tag <binding>"); } currentBindingName = atts.getValue("name"); } else if ("uri".equals(localName) || "bnode".equals(localName) || "literal".equals(localName)) { if (readingValue) { throw new SAXException("unexpected tag <" + localName + ">"); } lang = atts.getValue("http://www.w3.org/XML/1998/namespace", "lang"); readingValue = true; valueWriter = new StringWriter(); } } //System.out.println(namespaceURI); //System.out.println(qName); } @Override public void characters(char[] chars, int start, int length) throws SAXException { if (readingValue) { valueWriter.write(chars, start, length); //System.err.println(value + start + ", " + length); } } @Override public void endElement(String namespaceURI, String localName, String qName) throws SAXException { if ("http://www.w3.org/2005/sparql-results#".equals(namespaceURI)) { if ("result".equals(localName)) { results.add(currentResult); currentResult = null; } else if ("binding".equals(localName)) { if (currentBindingName == null) { throw new SAXException("unexpected tag </binding>"); } currentBindingName = null; } else { try { BindingType b = BindingType.valueOf(localName); RDFTerm rdfTerm = null; final Language language = lang == null ? null : new Language(lang); ; switch (b) { case uri: rdfTerm = new IRI(valueWriter.toString()); valueWriter = null; break; case bnode: rdfTerm = getBNode(valueWriter.toString()); valueWriter = null; break; case literal: final String lf = valueWriter.toString(); rdfTerm = new AbstractLiteral() { @Override public String getLexicalForm() { return lf; } @Override public IRI getDataType() { if (language != null) { return RDF_LANG_STRING; } //TODO implement return XSD_STRING; } @Override public Language getLanguage() { return language; } }; break; } currentResult.put(currentBindingName, rdfTerm); readingValue = false; } catch (IllegalArgumentException e) { //not uri|bnode|literal } } } } public void endDocument() throws SAXException { //System.out.println("results: " + results.size()); } } }