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.IOException; import java.io.InputStream; import java.util.HashSet; import java.util.Map; import java.util.Set; import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.xpath.XPathConstants; import javax.xml.xpath.XPathExpressionException; import javax.xml.xpath.XPathFactory; import org.alfresco.error.AlfrescoRuntimeException; 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.w3c.dom.Document; /** * A selector that executes a set of XPath statements against the XML document to determine * which content worker to provide. The XPath rules are simple, i.e. if an XML node is * found by the XPath statement, then it is considered to be a hit and the corresponding * worker is returned. * <p> * Currently, the only namespaces supported are those contained in the XML documents being * tested. * * @since 2.1 * @author Derek Hulley */ public class XPathContentWorkerSelector<W extends ContentWorker> implements ContentWorkerSelector { private static Log logger = LogFactory.getLog(XPathContentWorkerSelector.class); private DocumentBuilder documentBuilder; private XPathFactory xpathFactory; private Set<String> supportedMimetypes; private Map<String, W> workersByXPath; public XPathContentWorkerSelector() { try { documentBuilder = DocumentBuilderFactory.newInstance().newDocumentBuilder(); xpathFactory = XPathFactory.newInstance(); } catch (Throwable e) { throw new AlfrescoRuntimeException("Failed to initialize XPathContentWorkerSelector", e); } supportedMimetypes = new HashSet<String>(); supportedMimetypes.add(MimetypeMap.MIMETYPE_XML); } @Override public String toString() { StringBuilder sb = new StringBuilder(50); sb.append("XPathContentWorkerSelector").append("[ workers=").append(workersByXPath).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 use. All the XPath statements provided must be compatible with * a return value of type {@linkplain XPathConstants#NODE NODE}. * * @param workers a map of {@linkplain ContentWorker} instances * keyed by XPath statements */ public void setWorkers(Map<String, W> workers) { this.workersByXPath = workers; } /** * Checks the configuration. */ public void init() { PropertyCheck.mandatory(this, "workers", workersByXPath); PropertyCheck.mandatory(this, "supportedMimetypes", supportedMimetypes); } /** * Execute the XPath statements, in order, against the document. Any statements that fail * to run will be ignored. */ public W getWorker(ContentReader reader) { if (!supportedMimetypes.contains(reader.getMimetype())) { return null; } W worker = null; InputStream is = null; String xpath = null; try { is = reader.getContentInputStream(); Document doc = documentBuilder.parse(is); // Execute the statements worker = processDocument(doc); } catch (Throwable e) { throw new ContentIOException("\n" + "Failed to XPaths against XML document: \n" + " Reader: " + reader + "\n" + " Selector: " + this, e); } finally { if (is != null) { try { is.close(); } catch (IOException e) { } } } // Done if (logger.isDebugEnabled()) { logger.debug("\n" + "Chosen content worker for reader: \n" + " Reader: " + reader + "\n" + " XPath: " + xpath + "\n" + " Worker: " + worker); } return worker; } /** * Check the given document against the list of XPath statements provided. * * @param doc the XML document * @return Returns a content worker that was matched or <tt>null</tt> */ private W processDocument(Document doc) { for (Map.Entry<String, W> entry : workersByXPath.entrySet()) { try { String xpath = entry.getKey(); W worker = entry.getValue(); // Execute the statement Object ret = xpathFactory.newXPath().evaluate(xpath, doc, XPathConstants.NODE); if (ret != null) { // We found one return worker; } } catch (XPathExpressionException e) { // We accept this and move on } } // Nothing found return null; } }