Java tutorial
/** * Copyright 2009, 2010 The Regents of the University of California * Licensed under the Educational Community 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.osedu.org/licenses/ECL-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.opencastproject.caption.converters; import org.opencastproject.caption.api.Caption; import org.opencastproject.caption.api.CaptionConverter; import org.opencastproject.caption.api.CaptionConverterException; import org.opencastproject.caption.api.IllegalTimeFormatException; import org.opencastproject.caption.api.Time; import org.opencastproject.caption.impl.CaptionImpl; import org.opencastproject.caption.impl.TimeImpl; import org.opencastproject.caption.util.TimeUtil; import org.apache.commons.io.IOUtils; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.w3c.dom.Document; import org.w3c.dom.Element; import org.w3c.dom.Node; import org.w3c.dom.NodeList; import org.xml.sax.Attributes; import org.xml.sax.SAXException; import org.xml.sax.helpers.DefaultHandler; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.io.OutputStreamWriter; import java.util.ArrayList; import java.util.LinkedList; import java.util.List; import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.parsers.ParserConfigurationException; import javax.xml.parsers.SAXParser; import javax.xml.parsers.SAXParserFactory; import javax.xml.transform.Transformer; import javax.xml.transform.TransformerConfigurationException; import javax.xml.transform.TransformerException; import javax.xml.transform.TransformerFactory; import javax.xml.transform.dom.DOMSource; import javax.xml.transform.stream.StreamResult; /** * This is converter for DFXP, XML based caption format. DOM parser is used for both caption importing and exporting, * while SAX parser is used for determining which languages are present (DFXP can contain multiple languages). */ public class DFXPCaptionConverter implements CaptionConverter { /** logging utility */ private static final Logger logger = LoggerFactory.getLogger(DFXPCaptionConverter.class); private static final String EXTENSION = "dfxp.xml"; /** * {@inheritDoc} Parser used for parsing XML document is DOM parser. Language parameter will determine which language * is searched for and parsed. If there is no matching language, empty collection is returned. If language parameter * is <code>null</code> first language found is parsed. * * @see org.opencastproject.caption.api.CaptionConverter#importCaption(java.io.InputStream, java.lang.String) */ @Override public List<Caption> importCaption(InputStream in, String language) throws CaptionConverterException { // create new collection List<Caption> collection = new ArrayList<Caption>(); Document doc; try { DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); DocumentBuilder builder = factory.newDocumentBuilder(); doc = builder.parse(in); doc.getDocumentElement().normalize(); } catch (ParserConfigurationException e) { throw new CaptionConverterException("Could not parse captions", e); } catch (SAXException e) { throw new CaptionConverterException("Could not parse captions", e); } catch (IOException e) { throw new CaptionConverterException("Could not parse captions", e); } // get all <div> elements since they contain information about language NodeList divElements = doc.getElementsByTagName("div"); Element targetDiv = null; if (language != null) { // find first <div> element with matching language for (int i = 0; i < divElements.getLength(); i++) { Element n = (Element) divElements.item(i); if (n.getAttribute("xml:lang").equals(language)) { targetDiv = n; break; } } } else { if (divElements.getLength() > 1) { // more than one existing <div> element, no language specified logger.warn("More than one <div> element available. Parsing first one..."); } if (divElements.getLength() != 0) { targetDiv = (Element) divElements.item(0); } } // check if we found node if (targetDiv == null) { logger.warn("No suitable <div> element found for language {}", language); } else { NodeList pElements = targetDiv.getElementsByTagName("p"); // initialize start time Time time = null; try { time = new TimeImpl(0, 0, 0, 0); } catch (IllegalTimeFormatException e1) { } for (int i = 0; i < pElements.getLength(); i++) { try { Caption caption = parsePElement((Element) pElements.item(i)); // check time if (caption.getStartTime().compareTo(time) < 0 || caption.getStopTime().compareTo(caption.getStartTime()) <= 0) { logger.warn("Caption with invalid time encountered. Skipping..."); continue; } collection.add(caption); } catch (IllegalTimeFormatException e) { logger.warn("Caption with invalid time format encountered. Skipping..."); } } } // return collection return collection; } /** * Parse <p> element which contains one caption. * * @param p * <p> element to be parsed * @return new {@link Caption} object * @throws IllegalTimeFormatException * if time format does not match with expected format for DFXP */ private Caption parsePElement(Element p) throws IllegalTimeFormatException { Time begin = TimeUtil.importDFXP(p.getAttribute("begin").trim()); Time end = TimeUtil.importDFXP(p.getAttribute("end").trim()); // FIXME add logic for duration if end is absent // get text inside p String[] textArray = getTextCore(p).split("\n"); return new CaptionImpl(begin, end, textArray); } /** * Returns caption text stripped of all tags. * * @param p * <p> element to be parsed * @return Caption text with \n as new line character */ private String getTextCore(Node p) { StringBuffer captionText = new StringBuffer(); // get children NodeList list = p.getChildNodes(); for (int i = 0; i < list.getLength(); i++) { if (list.item(i).getNodeType() == Node.TEXT_NODE) { captionText.append(list.item(i).getTextContent()); } else if ("br".equals(list.item(i).getNodeName())) { captionText.append("\n"); } else { captionText.append(getTextCore(list.item(i))); } } return captionText.toString().trim(); } /** * {@inheritDoc} DOM parser is used to parse template from which whole document is then constructed. */ @Override public void exportCaption(OutputStream outputStream, List<Caption> captions, String language) throws IOException { // get document builder factory and parse template DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); Document doc = null; InputStream is = null; try { DocumentBuilder builder = factory.newDocumentBuilder(); // load dfxp template from file is = DFXPCaptionConverter.class.getResourceAsStream("/templates/template.dfxp.xml"); doc = builder.parse(is); } catch (ParserConfigurationException e) { // should not happen throw new RuntimeException(e); } catch (SAXException e) { // should not happen unless template is invalid throw new RuntimeException(e); } catch (IOException e) { // should not happen throw new RuntimeException(e); } finally { IOUtils.closeQuietly(is); } // retrieve body element Node bodyNode = doc.getElementsByTagName("body").item(0); // create new div element with specified language Element divNode = doc.createElement("div"); divNode.setAttribute("xml:lang", language != null ? language : "und"); bodyNode.appendChild(divNode); // update document for (Caption caption : captions) { Element newNode = doc.createElement("p"); newNode.setAttribute("begin", TimeUtil.exportToDFXP(caption.getStartTime())); newNode.setAttribute("end", TimeUtil.exportToDFXP(caption.getStopTime())); String[] captionText = caption.getCaption(); // text part newNode.appendChild(doc.createTextNode(captionText[0])); for (int i = 1; i < captionText.length; i++) { newNode.appendChild(doc.createElement("br")); newNode.appendChild(doc.createTextNode(captionText[i])); } divNode.appendChild(newNode); } // initialize stream writer OutputStreamWriter osw = new OutputStreamWriter(outputStream, "UTF-8"); StreamResult result = new StreamResult(osw); DOMSource source = new DOMSource(doc); TransformerFactory tfactory = TransformerFactory.newInstance(); Transformer transformer; try { transformer = tfactory.newTransformer(); transformer.transform(source, result); osw.flush(); } catch (TransformerConfigurationException e) { // should not happen throw new RuntimeException(e); } catch (TransformerException e) { // should not happen throw new RuntimeException(e); } finally { IOUtils.closeQuietly(osw); } } /** * {@inheritDoc} Uses SAX parser to quickly read the document and retrieve available languages. * * @see org.opencastproject.caption.api.CaptionConverter#getLanguageList(java.io.InputStream) */ @Override public String[] getLanguageList(InputStream input) throws CaptionConverterException { // create lang list final List<String> langList = new LinkedList<String>(); // get SAX parser SAXParserFactory factory = SAXParserFactory.newInstance(); try { SAXParser parser = factory.newSAXParser(); // create handler DefaultHandler handler = new DefaultHandler() { @Override public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException { if ("div".equals(qName)) { // we found div tag - let's make a lookup for language String lang = attributes.getValue("xml:lang"); if (lang == null) { // should never happen logger.warn("Missing xml:lang attribute for div element."); } else if (langList.contains(lang)) { logger.warn("Multiple div elements with same language."); } else { langList.add(lang); } } } }; // parse stream parser.parse(input, handler); } catch (ParserConfigurationException e) { // should not happen throw new RuntimeException(e); } catch (SAXException e) { throw new CaptionConverterException("Could not parse captions", e); } catch (IOException e) { throw new RuntimeException(e); } return langList.toArray(new String[0]); } /** * {@inheritDoc} * * @see org.opencastproject.caption.api.CaptionConverter#getExtension() */ @Override public String getExtension() { return EXTENSION; } }