Java tutorial
/** * 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 org.apache.marmotta.ldclient.provider.xml; import org.apache.marmotta.commons.sesame.model.Namespaces; import org.apache.marmotta.ldclient.exception.DataRetrievalException; import org.apache.marmotta.ldclient.provider.xml.mapping.XPathValueMapper; import org.apache.marmotta.ldclient.services.provider.AbstractHttpProvider; import org.jdom2.*; import org.jdom2.Namespace; import org.jdom2.input.SAXBuilder; import org.jdom2.input.sax.XMLReaders; import org.jdom2.xpath.XPathExpression; import org.openrdf.model.*; import org.openrdf.model.impl.ValueFactoryImpl; import java.io.IOException; import java.io.InputStream; import java.util.*; /** * Abstract implementation of a data provider based on XML documents. Implementing classes need to provide * a mapping table mapping from RDF property URIs to XPath Value Mappers that are evaluated on the XML document * (getXPathMappings method), as well as a list of URIs used as types for the created resource. * <p/> * Author: Sebastian Schaffert */ public abstract class AbstractXMLDataProvider extends AbstractHttpProvider { /** * Return a mapping table mapping from RDF properties to XPath Value Mappers. Each entry in the map is evaluated * in turn; in case the XPath expression yields a result, the property is added for the processed resource. * * @return * @param requestUrl */ protected abstract Map<String, XPathValueMapper> getXPathMappings(String requestUrl); /** * Return a list of URIs that should be added as types for each processed resource. * * @return * @param resource */ protected abstract List<String> getTypes(URI resource); /** * Provide namespace mappings for the XPath expressions from namespace prefix to namespace URI. May be overridden * by subclasses as appropriate, the default implementation returns an empty map. * * @return */ protected Map<String, String> getNamespaceMappings() { return Collections.emptyMap(); } /** * Parse the HTTP response entity returned by the web service call and return its contents as a Sesame RDF * repository. The content type returned by the web service is passed as argument to help the implementation * decide how to parse the data. * * * * @param resource the subject of the data retrieval * @param triples *@param in input stream as returned by the remote webservice * @param contentType content type as returned in the HTTP headers of the remote webservice @return an RDF repository containing an RDF representation of the dataset located at the remote resource. * @throws java.io.IOException in case an error occurs while reading the input stream */ @Override public List<String> parseResponse(String resource, String requestUrl, Model triples, InputStream in, String contentType) throws DataRetrievalException { // build a JDOM document try { SAXBuilder parser = new SAXBuilder(XMLReaders.NONVALIDATING); Document doc = parser.build(in); Set<Namespace> namespaces = new HashSet<Namespace>(); for (Map.Entry<String, String> ns : getNamespaceMappings().entrySet()) { namespaces.add(Namespace.getNamespace(ns.getKey(), ns.getValue())); } ValueFactory vf = new ValueFactoryImpl(); Resource subject = vf.createURI(resource); for (Map.Entry<String, XPathValueMapper> mapping : getXPathMappings(requestUrl).entrySet()) { XPathExpression<Object> xpath = mapping.getValue().getCompiled(); org.openrdf.model.URI predicate = triples.getValueFactory().createURI(mapping.getKey()); for (Object value : xpath.evaluate(doc)) { String str_value; if (value instanceof Element) { str_value = ((Element) value).getValue(); } else if (value instanceof Text) { str_value = ((Text) value).getValue(); } else if (value instanceof Attribute) { str_value = ((Attribute) value).getValue(); } else if (value instanceof CDATA) { str_value = ((CDATA) value).getValue(); } else if (value instanceof Comment) { str_value = ((Comment) value).getValue(); } else { str_value = value.toString(); } List<Value> objects = mapping.getValue().map(resource, str_value, triples.getValueFactory()); for (Value object : objects) { Statement stmt = triples.getValueFactory().createStatement(subject, predicate, object); triples.add(stmt); } } } org.openrdf.model.URI ptype = triples.getValueFactory().createURI(Namespaces.NS_RDF + "type"); for (String typeUri : getTypes(vf.createURI(resource))) { Resource type_resource = vf.createURI(typeUri); triples.add(vf.createStatement(subject, ptype, type_resource)); } return Collections.emptyList(); } catch (JDOMException e) { throw new DataRetrievalException("could not parse XML response. It is not in proper XML format", e); } catch (IOException e) { throw new DataRetrievalException("I/O error while parsing XML response", e); } } }