Java tutorial
/* * Copyright 2009 GBIF. 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 net.sibcolombia.sibsp.model.factory; import java.io.IOException; import java.io.InputStream; import java.util.Collection; import java.util.LinkedList; import java.util.List; import javax.xml.parsers.ParserConfigurationException; import javax.xml.parsers.SAXParserFactory; import com.google.inject.Inject; import com.google.inject.Singleton; import net.sibcolombia.sibsp.model.Extension; import net.sibcolombia.sibsp.model.ExtensionProperty; import org.apache.commons.digester.Digester; import org.apache.http.HttpEntity; import org.apache.http.HttpResponse; import org.apache.http.client.HttpClient; import org.apache.http.client.methods.HttpGet; import org.apache.http.impl.client.DefaultHttpClient; import org.apache.log4j.Logger; import org.xml.sax.SAXException; /** * Building from XML definitions. Because an extension can reference thesauri, this is a 2 pass parsing process. * <p/> * * <pre> * - the first pass looks for thesauri, that need built * - these are built, and then a map<thesaurusURL, Vocabulary> is put onto the root of the second parse stack * - this map is then used to get the Vocabulary in the second pass of parsing * </pre> */ @Singleton public class ExtensionFactory { private static final Logger LOG = Logger.getLogger(ExtensionFactory.class); public static final String EXTENSION_NAMESPACE = "http://rs.gbif.org/extension/"; private final ThesaurusHandlingRule thesaurusRule; private final SAXParserFactory saxf; private final HttpClient client; @Inject public ExtensionFactory(ThesaurusHandlingRule thesaurusRule, SAXParserFactory factory, DefaultHttpClient client) { this.thesaurusRule = thesaurusRule; this.saxf = factory; this.client = client; } /** * Builds extensions from the supplied Strings which should be URLs. * * @param urls To build extensions from * @return The collection of Extensions */ public Collection<Extension> build(Collection<String> urls) { List<Extension> extensions = new LinkedList<Extension>(); for (String urlAsString : urls) { try { Extension e = build(urlAsString); if (e != null) { extensions.add(e); } } catch (IOException e) { LOG.error("Unable to access extension definition defined at " + urlAsString, e); } catch (SAXException e) { LOG.error("Unable to parse extension definition defined at " + urlAsString, e); } } return extensions; } /** * Builds an extension from the supplied input stream. * * @param is For the XML * @return The extension */ public Extension build(InputStream is) throws IOException, SAXException, ParserConfigurationException { // in order to deal with arbitrary namespace prefixes we need to parse namespace aware! Digester digester = new Digester(saxf.newSAXParser()); digester.setRuleNamespaceURI(EXTENSION_NAMESPACE); Extension e = new Extension(); digester.push(e); digester.addCallMethod("*/extension", "setTitle", 1); digester.addRule("*/extension", new CallParamNoNSRule(0, "title")); digester.addCallMethod("*/extension", "setName", 1); digester.addCallParam("*/extension", 0, "name"); digester.addCallMethod("*/extension", "setNamespace", 1); digester.addCallParam("*/extension", 0, "namespace"); digester.addCallMethod("*/extension", "setRowType", 1); digester.addCallParam("*/extension", 0, "rowType"); digester.addCallMethod("*/extension", "setLink", 1); digester.addRule("*/extension", new CallParamNoNSRule(0, "relation")); digester.addCallMethod("*/extension", "setDescription", 1); digester.addRule("*/extension", new CallParamNoNSRule(0, "description")); digester.addCallMethod("*/extension", "setSubject", 1); digester.addRule("*/extension", new CallParamNoNSRule(0, "subject")); // build the properties digester.addObjectCreate("*/property", ExtensionProperty.class); digester.addCallMethod("*/property", "setQualname", 1); digester.addCallParam("*/property", 0, "qualName"); digester.addCallMethod("*/property", "setName", 1); digester.addCallParam("*/property", 0, "name"); digester.addCallMethod("*/property", "setNamespace", 1); digester.addCallParam("*/property", 0, "namespace"); digester.addCallMethod("*/property", "setGroup", 1); digester.addCallParam("*/property", 0, "group"); digester.addCallMethod("*/property", "setRequired", 1); digester.addCallParam("*/property", 0, "required"); digester.addCallMethod("*/property", "setLink", 1); digester.addRule("*/property", new CallParamNoNSRule(0, "relation")); digester.addCallMethod("*/property", "setDescription", 1); digester.addRule("*/property", new CallParamNoNSRule(0, "description")); digester.addCallMethod("*/property", "setExamples", 1); digester.addCallParam("*/property", 0, "examples"); digester.addCallMethod("*/property", "setType", 1); digester.addCallParam("*/property", 0, "type"); // This is a special rule that will use the url2ThesaurusMap // to set the Vocabulary based on the attribute "thesaurus" digester.addRule("*/property", thesaurusRule); digester.addSetNext("*/property", "addProperty"); digester.parse(is); return e; } /** * Builds an extension from the supplied input stream * * @param url For the XML * @return The extension */ public Extension build(String url) throws IOException, SAXException { HttpGet get = new HttpGet(url); // execute try { HttpResponse response = client.execute(get); HttpEntity entity = response.getEntity(); if (entity != null) { // copy stream to local file InputStream is = entity.getContent(); try { Extension e = build(is); LOG.info("Successfully parsed extension: " + e.getTitle()); return e; } catch (SAXException e) { LOG.error("Unable to parse XML for extension: " + e.getMessage(), e); } finally { is.close(); } entity.consumeContent(); } } catch (Exception e) { LOG.error(e); } // close http connection return null; } }