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.oodt.cas.product.rdf; //JDK imports import org.apache.commons.lang.StringEscapeUtils; import org.apache.commons.lang.StringUtils; import org.apache.commons.lang.WordUtils; import org.apache.oodt.cas.filemgr.structs.ProductType; import org.apache.oodt.cas.filemgr.structs.exceptions.ConnectionException; import org.apache.oodt.cas.filemgr.structs.exceptions.RepositoryManagerException; import org.apache.oodt.cas.filemgr.system.XmlRpcFileManagerClient; import org.apache.oodt.cas.metadata.util.PathUtils; import org.apache.oodt.commons.xml.XMLUtils; import org.w3c.dom.Document; import org.w3c.dom.Element; import java.io.FileNotFoundException; import java.io.IOException; import java.net.MalformedURLException; import java.net.URL; import java.util.List; import java.util.Vector; import java.util.logging.Level; import java.util.logging.Logger; import javax.servlet.ServletConfig; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.parsers.ParserConfigurationException; import javax.xml.transform.Transformer; import javax.xml.transform.TransformerException; import javax.xml.transform.TransformerFactory; import javax.xml.transform.dom.DOMSource; import javax.xml.transform.stream.StreamResult; //OODT imports /** * * A Servlet that exports ProductType metaata information using the <a * href="http://www.w3.org">W3C's</a> <a href="http://www.w3.org/RDF/"> Resource * Description Framework</a>. * * @author mattmann * @version $Revision$ * * */ public class RDFDatasetServlet extends HttpServlet { /* serial Version UID */ private static final long serialVersionUID = -3660991271642533985L; /* our client to the file manager */ private XmlRpcFileManagerClient fClient = null; /* our log stream */ private Logger LOG = Logger.getLogger(RDFProductServlet.class.getName()); /* our RDF configuration */ private RDFConfig rdfConf; /** * <p> * Default Constructor * </p> * . */ public RDFDatasetServlet() { } /** * Initializes the servlet. */ public void init(ServletConfig config) throws ServletException { super.init(config); try { this.rdfConf = RDFUtils.initRDF(config); } catch (FileNotFoundException e) { LOG.log(Level.SEVERE, e.getMessage()); throw new ServletException(e.getMessage()); } String fileManagerUrl; try { fileManagerUrl = PathUtils .replaceEnvVariables(config.getServletContext().getInitParameter("filemgr.url")); } catch (Exception e) { throw new ServletException("Failed to get filemgr url : " + e.getMessage(), e); } fClient = null; try { fClient = new XmlRpcFileManagerClient(new URL(fileManagerUrl)); } catch (MalformedURLException e) { LOG.log(Level.SEVERE, "Unable to initialize file manager url in RDF Servlet: [url=" + fileManagerUrl + "], Message: " + e.getMessage()); } catch (ConnectionException e) { LOG.log(Level.SEVERE, "Unable to initialize file manager url in RDF Servlet: [url=" + fileManagerUrl + "], Message: " + e.getMessage()); } } public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, java.io.IOException { doIt(req, resp); } public void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, java.io.IOException { doIt(req, resp); } public void doIt(HttpServletRequest req, HttpServletResponse resp) throws ServletException { // need to know the type of product to get products for String productTypeName = req.getParameter("type"); String productTypeId = req.getParameter("typeID"); ProductTypeFilter filter = new ProductTypeFilter(req.getParameter("filter")); ProductType type; List<ProductType> productTypes = new Vector<ProductType>(); if (productTypeName.equals("ALL")) { productTypes = safeGetProductTypes(); } else { try { type = fClient.getProductTypeById(productTypeId); productTypes.add(type); } catch (RepositoryManagerException e) { LOG.log(Level.SEVERE, "Unable to obtain product type from product type id: [" + productTypeId + "]: Message: " + e.getMessage()); return; } } String requestUrl = req.getRequestURL().toString(); String origBase = requestUrl.substring(0, requestUrl.lastIndexOf('/')); String base = origBase.substring(0, origBase.lastIndexOf('/')) + "/dataset"; // allow override through the "baseUrl" GET parameter if (req.getParameter("baseUrl") != null) { base = req.getParameter("baseUrl"); } if (productTypes != null && productTypes.size() > 0) { List<ProductType> subsetList = new Vector<ProductType>(); // perform filtering for (ProductType pt : productTypes) { if (filter.filter(pt)) { subsetList.add(pt); } } outputRDF(subsetList, base, resp); } } public void outputRDF(List<ProductType> productTypes, String base, HttpServletResponse resp) throws ServletException { try { DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); factory.setNamespaceAware(true); Document doc = factory.newDocumentBuilder().newDocument(); Element rdf = XMLUtils.addNode(doc, doc, "rdf:RDF"); RDFUtils.addNamespaces(doc, rdf, this.rdfConf); for (ProductType type : productTypes) { Element productTypeRdfDesc = XMLUtils.addNode(doc, rdf, this.rdfConf.getTypeNs(type.getName()) + ":" + type.getName()); XMLUtils.addAttribute(doc, productTypeRdfDesc, "rdf:about", base + "?typeID=" + type.getProductTypeId()); // for all of its metadata keys and values, loop through them // and add RDF nodes underneath the RdfDesc for this product if (type.getTypeMetadata() != null) { for (String key : type.getTypeMetadata().getMap().keySet()) { List<String> vals = type.getTypeMetadata().getAllMetadata(key); if (vals != null && vals.size() > 0) { for (String val : vals) { //OODT-665 fix, take keys like //PRODUCT Experiment Type //and transform it into ProductExperimentType String outputKey = key; if (outputKey.contains(" ")) { outputKey = StringUtils.join(WordUtils.capitalizeFully(outputKey).split(" ")); } val = StringEscapeUtils.escapeXml(val); Element rdfElem = RDFUtils.getRDFElement(outputKey, val, this.rdfConf, doc); productTypeRdfDesc.appendChild(rdfElem); } } } } } DOMSource source = new DOMSource(doc); TransformerFactory transFactory = TransformerFactory.newInstance(); Transformer transformer = transFactory.newTransformer(); transformer.setOutputProperty("indent", "yes"); StreamResult result = new StreamResult(resp.getOutputStream()); resp.setContentType("text/xml"); transformer.transform(source, result); } catch (ParserConfigurationException e) { throw new ServletException(e); } catch (TransformerException e) { throw new ServletException(e); } catch (IOException e) { throw new ServletException(e); } } private List<ProductType> safeGetProductTypes() { List<ProductType> types = null; try { types = fClient.getProductTypes(); } catch (RepositoryManagerException e) { LOG.log(Level.SEVERE, e.getMessage()); LOG.log(Level.WARNING, "Error retrieving product types: Message: " + e.getMessage()); } return types; } }