Java tutorial
/** * This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at http://mozilla.org/MPL/2.0/. * * Copyright (C) 2012, 2013 Pyravlos Team * * http://www.strabon.di.uoa.gr/ */ package eu.earthobservatory.org.StrabonEndpoint.client; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.net.URL; import java.nio.charset.Charset; import java.util.ArrayList; import java.util.List; import org.apache.commons.httpclient.params.HostParams; import org.apache.commons.httpclient.params.HttpMethodParams; import org.apache.commons.httpclient.params.HttpParams; import org.apache.http.HttpEntity; import org.apache.http.HttpResponse; import org.apache.http.NameValuePair; import org.apache.http.client.entity.UrlEncodedFormEntity; import org.apache.http.client.methods.HttpPost; import org.apache.http.entity.StringEntity; import org.apache.http.message.BasicNameValuePair; import org.apache.xerces.impl.dv.util.Base64; import org.openrdf.query.resultio.TupleQueryResultFormat; import org.openrdf.query.resultio.stSPARQLQueryResultFormat; import org.openrdf.rio.RDFFormat; /** * This class is the implementation of a java client for accessing * SPARQLEndpoint instances. * * @author Charalampos Nikolaou <charnik@di.uoa.gr> * @author Kallirroi Dogani <kallirroi@di.uoa.gr. */ public class SPARQLEndpoint extends HTTPClient { public SPARQLEndpoint(String host, int port) { super(host, port); } public SPARQLEndpoint(String host, int port, String endpointName) { super(host, port, endpointName); } /** * Executes a SPARQL query on the Endpoint and get the results * in the format specified by stSPARQLQueryResultFormat, which is * an instance of class (or a subclass) {@link TupleQueryResultFormat}. * * @param sparqlQuery * @param format * @return * @throws IOException */ public EndpointResult query(String sparqlQuery, stSPARQLQueryResultFormat format) throws IOException { assert (format != null); // create a post method to execute HttpPost method = new HttpPost(getConnectionURL()); // set the query parameter List<NameValuePair> params = new ArrayList<NameValuePair>(); params.add(new BasicNameValuePair("query", sparqlQuery)); UrlEncodedFormEntity encodedEntity = new UrlEncodedFormEntity(params, Charset.defaultCharset()); method.setEntity(encodedEntity); // set the content type method.setHeader("Content-Type", "application/x-www-form-urlencoded"); // set the accept format method.addHeader("Accept", format.getDefaultMIMEType()); try { // response that will be filled next String responseBody = ""; // execute the method HttpResponse response = hc.execute(method); int statusCode = response.getStatusLine().getStatusCode(); // If the response does not enclose an entity, there is no need // to worry about connection release HttpEntity entity = response.getEntity(); if (entity != null) { InputStream instream = entity.getContent(); try { BufferedReader reader = new BufferedReader(new InputStreamReader(instream)); StringBuffer strBuf = new StringBuffer(); // do something useful with the response String nextLine; while ((nextLine = reader.readLine()) != null) { strBuf.append(nextLine + "\n"); } // remove last newline character if (strBuf.length() > 0) { strBuf.setLength(strBuf.length() - 1); } responseBody = strBuf.toString(); } catch (IOException ex) { // In case of an IOException the connection will be released // back to the connection manager automatically throw ex; } catch (RuntimeException ex) { // In case of an unexpected exception you may want to abort // the HTTP request in order to shut down the underlying // connection and release it back to the connection manager. method.abort(); throw ex; } finally { // Closing the input stream will trigger connection release instream.close(); } } return new EndpointResult(statusCode, response.getStatusLine().getReasonPhrase(), responseBody); } catch (IOException e) { throw e; } finally { // release the connection. method.releaseConnection(); } } /* Functions 'store' and 'update' do not follow the SPARQL Protocol. * This means that only Strabon Endpoint supports these operations. * In future they must be modified in order to be compatible with * Virtuso and Parliament endpoints. */ /** * Stores the RDF <code>data</code> which are in the RDF format * <code>format</code> in the named graph specified by the URL * <code>namedGraph</code>. * * @param data * @param format * @param namedGraph * @return <code>true</code> if store was successful, <code>false</code> otherwise * @throws IOException */ public boolean store(String data, RDFFormat format, URL namedGraph) throws IOException { assert (format != null); // create a post method to execute HttpPost method = new HttpPost(getConnectionURL()); // set the url and fromurl parameters List<NameValuePair> params = new ArrayList<NameValuePair>(); params.add(new BasicNameValuePair("data", data)); if (namedGraph != null) params.add(new BasicNameValuePair("graph", namedGraph.toString())); UrlEncodedFormEntity encodedEntity = new UrlEncodedFormEntity(params, Charset.defaultCharset()); method.setEntity(encodedEntity); // set the content type method.setHeader("Content-Type", "application/x-www-form-urlencoded"); // set the accept format method.addHeader("Accept", format.getDefaultMIMEType()); //set username and password if (getUser() != null && getPassword() != null) { String userPass = getUser() + ":" + getPassword(); String encoding = Base64.encode(userPass.getBytes()); method.setHeader("Authorization", "Basic " + encoding); } try { // response that will be filled next // String responseBody = ""; // execute the method HttpResponse response = hc.execute(method); int statusCode = response.getStatusLine().getStatusCode(); if (statusCode == 200) return true; else { System.err.println("Status code " + statusCode); return false; } } catch (IOException e) { throw e; } finally { // release the connection. method.releaseConnection(); } } /** * Stores the RDF data located at <code>data</code> which are in the * RDF format <code>format</code> in the named graph specified by the * URL <code>namedGraph</code>. * * @param data * @param format * @param namedGraph * @return <code>true</code> if store was successful, <code>false</code> otherwise */ /* * Comment: in order to make queries to strabon endpoint we must create a SPARQLEndpoint * with endpointName ".../Query". To store data to strabon endpoint the endpointName of * SPARQLEndpoint must be something like ".../Store". This means that the same object of * SPARQLEndpoint cannot execute store and query operations for strabon endpoints. * This is wrong and must be fixed. Also, the main idea is that the SPARQLEndpoint client * should be a general endpoint client that supports strabon, virtuoso and parliament endpoints. */ public boolean store(URL data, RDFFormat format, URL namedGraph) throws IOException { assert (format != null); // create a post method to execute HttpPost method = new HttpPost(getConnectionURL()); // set the url and fromurl parameters List<NameValuePair> params = new ArrayList<NameValuePair>(); params.add(new BasicNameValuePair("url", data.toString())); params.add(new BasicNameValuePair("fromurl", "")); if (namedGraph != null) params.add(new BasicNameValuePair("graph", namedGraph.toString())); UrlEncodedFormEntity encodedEntity = new UrlEncodedFormEntity(params, Charset.defaultCharset()); method.setEntity(encodedEntity); // set the content type method.setHeader("Content-Type", "application/x-www-form-urlencoded"); // set the accept format method.addHeader("Accept", format.getDefaultMIMEType()); //set username and password if (getUser() != null && getPassword() != null) { String userPass = getUser() + ":" + getPassword(); String encoding = Base64.encode(userPass.getBytes()); method.setHeader("Authorization", "Basic " + encoding); } try { // response that will be filled next // String responseBody = ""; // execute the method HttpResponse response = hc.execute(method); int statusCode = response.getStatusLine().getStatusCode(); if (statusCode == 200) return true; else { System.err.println("Status code " + statusCode); return false; } } catch (IOException e) { throw e; } finally { // release the connection. method.releaseConnection(); } } /** * Executes the SPARQL Update query specified in <code>sparqlUpdate</code>. * * @param sparqlUpdate * @return <code>true</code> if store was successful, <code>false</code> otherwise * @throws IOException */ public boolean update(String sparqlUpdate) throws IOException { // create a post method to execute HttpPost method = new HttpPost(getConnectionURL()); // set the query parameter List<NameValuePair> params = new ArrayList<NameValuePair>(); params.add(new BasicNameValuePair("query", sparqlUpdate)); UrlEncodedFormEntity encodedEntity = new UrlEncodedFormEntity(params, Charset.defaultCharset()); method.setEntity(encodedEntity); // set the content type method.setHeader("Content-Type", "application/x-www-form-urlencoded"); // set the accept format method.addHeader("Accept", "text/xml"); //set username and password if (getUser() != null && getPassword() != null) { String userPass = getUser() + ":" + getPassword(); String encoding = Base64.encode(userPass.getBytes()); method.setHeader("Authorization", "Basic " + encoding); } try { // response that will be filled next // execute the method HttpResponse response = hc.execute(method); int statusCode = response.getStatusLine().getStatusCode(); if (statusCode == 200) return true; else { System.err.println("Status code " + statusCode); return false; } } catch (IOException e) { throw e; } finally { // release the connection. method.releaseConnection(); } } public EndpointResult describe(String sparqlDescribe) { throw new UnsupportedOperationException(); } public EndpointResult construct(String sparqlConstruct) { throw new UnsupportedOperationException(); } public EndpointResult ask(String sparqlAsk) { throw new UnsupportedOperationException(); } public static void main(String args[]) { if (args.length < 4) { System.err.println( "Usage: eu.earthobservatory.org.StrabonEndpoint.client.SPARQLEndpoint <HOST> <PORT> <APPNAME> [<FORMAT>]"); System.err.println(" where <HOST> is the hostname of the Strabon Endpoint"); System.err.println(" <PORT> is the port to connect to on the host"); System.err.println( " <APPNAME> is the application name of Strabon Endpoint as deployed in the Tomcat container"); System.err.println(" <QUERY> is the query to execute on the endpoint"); System.err.println( " [<FORMAT>] is the format of your results. Should be one of XML (default), KML, KMZ, GeoJSON, TSV, or HTML."); System.exit(1); } String host = args[0]; Integer port = new Integer(args[1]); String appName = args[2]; String query = args[3]; String format = ""; if (args.length == 5) { format = args[4]; } else { format = "XML"; } SPARQLEndpoint endpoint = new SPARQLEndpoint(host, port, appName); try { EndpointResult result = endpoint.query(query, (stSPARQLQueryResultFormat) stSPARQLQueryResultFormat.valueOf(format)); System.out.println("Status code: " + result.getStatusCode()); System.out.println("Status text: " + result.getStatusText()); System.out.println("<----- Result ----->"); System.out.println(result.getResponse().replaceAll("\n", "\n\t")); System.out.println("<----- Result ----->"); } catch (IOException e) { e.printStackTrace(); } } }