Java tutorial
/* * #%L * Alfresco Repository * %% * Copyright (C) 2005 - 2016 Alfresco Software Limited * %% * This file is part of the Alfresco software. * If the software was purchased under a paid Alfresco license, the terms of * the paid license agreement will prevail. Otherwise, the software is * provided under the following open source license terms: * * Alfresco is free software: you can redistribute it and/or modify * it under the terms of the GNU Lesser General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * Alfresco is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public License * along with Alfresco. If not, see <http://www.gnu.org/licenses/>. * #L% */ package org.alfresco.repo.content.selector; import java.io.InputStream; import java.util.Collections; import java.util.HashSet; import java.util.Map; import java.util.Set; import javax.xml.parsers.SAXParser; import javax.xml.parsers.SAXParserFactory; import org.alfresco.repo.content.ContentWorker; import org.alfresco.repo.content.MimetypeMap; import org.alfresco.service.cmr.repository.ContentIOException; import org.alfresco.service.cmr.repository.ContentReader; import org.alfresco.util.PropertyCheck; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.xml.sax.Attributes; import org.xml.sax.SAXException; import org.xml.sax.helpers.DefaultHandler; /** * A selector that looks at the root node of an XML document to determine which worker to provide. * There are many ways to identify XML documents and this is probably the simplest. Alternate * implementations might execute a series of xpath statements or look for specific namespace * declarations in the document. The net result is the same, i.e. given an XML document, a * worker is provided to the caller. * * @since 2.1 * @author Derek Hulley */ public class RootElementNameContentWorkerSelector<W extends ContentWorker> extends DefaultHandler implements ContentWorkerSelector<ContentWorker> { private static Log logger = LogFactory.getLog(RootElementNameContentWorkerSelector.class); private SAXParserFactory saxParserFactory; private Set<String> supportedMimetypes; private Map<String, W> workersByRootElementName; public RootElementNameContentWorkerSelector() { saxParserFactory = SAXParserFactory.newInstance(); supportedMimetypes = new HashSet<String>(); supportedMimetypes.add(MimetypeMap.MIMETYPE_XML); workersByRootElementName = Collections.emptyMap(); } @Override public String toString() { StringBuilder sb = new StringBuilder(50); sb.append("RootElementNameContentWorkerSelector").append("[ workers=").append(workersByRootElementName) .append("]"); return sb.toString(); } /** * Optionally set the mimetypes supported. They must be XML formats that the chosen * parser will be able to handle. * * @param supportedMimetypes the list of mimetypes. The default is <b>text/xml</b>. */ public void setSupportedMimetypes(Set<String> supportedMimetypes) { this.supportedMimetypes = supportedMimetypes; } /** * Set the workers to choose from. * * @param workers a map of {@linkplain ContentWorker} instances * keyed by root element name */ public void setWorkers(Map<String, W> workers) { this.workersByRootElementName = workers; } /** * Checks the configuration. */ public void init() { PropertyCheck.mandatory(this, "workers", workersByRootElementName); PropertyCheck.mandatory(this, "supportedMimetypes", supportedMimetypes); } /** * Performs a match of the root element name to find the correct content worker. */ public W getWorker(ContentReader reader) { if (!supportedMimetypes.contains(reader.getMimetype())) { return null; } W worker = null; InputStream is = null; String rootElementName = null; try { is = reader.getContentInputStream(); SAXParser saxParser = saxParserFactory.newSAXParser(); saxParser.parse(is, this); // No match possible } catch (RootElementFoundException e) { rootElementName = e.getElementName(); worker = workersByRootElementName.get(rootElementName); } catch (Throwable e) { throw new ContentIOException("\n" + "Failed to extract root element from XML document: \n" + " Reader: " + reader + "\n" + " Selector: " + this, e); } finally { if (is != null) { try { is.close(); } catch (Throwable e) { } } } // Done if (logger.isDebugEnabled()) { logger.debug("\n" + "Chosen content worker for reader: \n" + " Reader: " + reader + "\n" + " Root Element: " + rootElementName + "\n" + " Worker: " + worker); } return worker; } @Override public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException { throw new RootElementFoundException(qName); } /** * An exception to break out of the XML parsing early */ private static class RootElementFoundException extends SAXException { private static final long serialVersionUID = 6845880422947198814L; private String elementName; public RootElementFoundException(String elementName) { super(elementName); this.elementName = elementName; } public String getElementName() { return elementName; } } }