Java tutorial
// Copyright 2006 Chibacon /* * * Artistic License * * Preamble * * The intent of this document is to state the conditions under which a * Package may be copied, such that the Copyright Holder maintains some * semblance of artistic control over the development of the package, * while giving the users of the package the right to use and distribute * the Package in a more-or-less customary fashion, plus the right to make * reasonable modifications. * * Definitions: * * "Package" refers to the collection of files distributed by the * Copyright Holder, and derivatives of that collection of files created * through textual modification. * * "Standard Version" refers to such a Package if it has not been * modified, or has been modified in accordance with the wishes of the * Copyright Holder. * * "Copyright Holder" is whoever is named in the copyright or copyrights * for the package. * * "You" is you, if you're thinking about copying or distributing this Package. * * "Reasonable copying fee" is whatever you can justify on the basis of * media cost, duplication charges, time of people involved, and so * on. (You will not be required to justify it to the Copyright Holder, * but only to the computing community at large as a market that must bear * the fee.) * * "Freely Available" means that no fee is charged for the item itself, * though there may be fees involved in handling the item. It also means * that recipients of the item may redistribute it under the same * conditions they received it. * * 1. You may make and give away verbatim copies of the source form of the * Standard Version of this Package without restriction, provided that you * duplicate all of the original copyright notices and associated * disclaimers. * * 2. You may apply bug fixes, portability fixes and other modifications * derived from the Public Domain or from the Copyright Holder. A Package * modified in such a way shall still be considered the Standard Version. * * 3. You may otherwise modify your copy of this Package in any way, * provided that you insert a prominent notice in each changed file * stating how and when you changed that file, and provided that you do at * least ONE of the following: * * a) place your modifications in the Public Domain or otherwise make * them Freely Available, such as by posting said modifications to * Usenet or an equivalent medium, or placing the modifications on a * major archive site such as ftp.uu.net, or by allowing the Copyright * Holder to include your modifications in the Standard Version of the * Package. * * b) use the modified Package only within your corporation or * organization. * * c) rename any non-standard executables so the names do not conflict * with standard executables, which must also be provided, and provide * a separate manual page for each non-standard executable that * clearly documents how it differs from the Standard Version. * * d) make other distribution arrangements with the Copyright Holder. * * 4. You may distribute the programs of this Package in object code or * executable form, provided that you do at least ONE of the following: * * a) distribute a Standard Version of the executables and library * files, together with instructions (in the manual page or * equivalent) on where to get the Standard Version. * * b) accompany the distribution with the machine-readable source of * the Package with your modifications. * * c) accompany any non-standard executables with their corresponding * Standard Version executables, giving the non-standard executables * non-standard names, and clearly documenting the differences in * manual pages (or equivalent), together with instructions on where * to get the Standard Version. * * d) make other distribution arrangements with the Copyright Holder. * * 5. You may charge a reasonable copying fee for any distribution of this * Package. You may charge any fee you choose for support of this * Package. You may not charge a fee for this Package itself. However, * you may distribute this Package in aggregate with other (possibly * commercial) programs as part of a larger (possibly commercial) software * distribution provided that you do not advertise this Package as a * product of your own. * * 6. The scripts and library files supplied as input to or produced as * output from the programs of this Package do not automatically fall * under the copyright of this Package, but belong to whomever generated * them, and may be sold commercially, and may be aggregated with this * Package. * * 7. C or perl subroutines supplied by you and linked into this Package * shall not be considered part of this Package. * * 8. The name of the Copyright Holder may not be used to endorse or * promote products derived from this software without specific prior * written permission. * * 9. THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF * MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. * */ package org.chiba.xml.xslt.impl; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.chiba.xml.xforms.exception.XFormsException; import org.chiba.xml.xslt.TransformerService; import javax.xml.transform.*; import javax.xml.transform.stream.StreamSource; import java.net.URI; import java.util.ArrayList; import java.util.HashMap; import java.util.List; /** * Provides a resource caching implmentation of TransformerService. Special * care is taken for the inter-dependencies of the cached resources, i.e. * a resource is considered dirty if any dependant resource is dirty. This * means that a stylesheet will be reloaded even if just an included stylesheet * has been changed. * * @author Ulrich Nicolas Lissé * @version $Id: CachingTransformerService.java,v 1.1 2009/02/17 09:00:54 civilis Exp $ */ public class CachingTransformerService implements TransformerService, URIResolver { private static final Log LOGGER = LogFactory.getLog(CachingTransformerService.class); private HashMap resources; private ArrayList resolvers; private TransformerFactory transformerFactory; /** * Creates a new caching transformer service. */ public CachingTransformerService() { this.resources = new HashMap(); this.resolvers = new ArrayList(); } /** * Creates a new caching transformer service. * * @param resolver a resource resolver. */ public CachingTransformerService(ResourceResolver resolver) { this(); addResourceResolver(resolver); } // implementation of 'org.chiba.xml.xslt.TransformerService' /** * Returns the transformer factory. * * @return the transformer factory. */ public TransformerFactory getTransformerFactory() { if (this.transformerFactory == null) { this.transformerFactory = TransformerFactory.newInstance(); this.transformerFactory.setURIResolver(this); } return this.transformerFactory; } /** * Sets the transformer factory. * * @param factory the transformer factory. */ public void setTransformerFactory(TransformerFactory factory) { this.transformerFactory = factory; if (this.transformerFactory != null) { this.transformerFactory.setURIResolver(this); } } /** * Returns an identity transformer. * * @return an identity transformer. * @throws TransformerException if the transformer couldn't be created. */ public Transformer getTransformer() throws TransformerException { if (LOGGER.isDebugEnabled()) { LOGGER.debug("get transformer: identity transformer"); } return getTransformerFactory().newTransformer(); } /** * Returns a transformer for the specified stylesheet. * <p/> * If the URI is null, an identity transformer is created. * * @param uri the URI identifying the stylesheet. * @return a transformer for the specified stylesheet. * @throws TransformerException if the transformer couldn't be created. */ public Transformer getTransformer(URI uri) throws TransformerException { if (uri == null) { return getTransformer(); } try { // lookup cache entry CacheEntry entry = (CacheEntry) this.resources.get(uri); if (entry == null || entry.isDirty()) { if (LOGGER.isDebugEnabled()) { LOGGER.debug("get transformer: cache " + (entry == null ? "miss" : "dirty") + " for " + uri); } // load missing/dirty resource Resource resource = load(uri); if (resource == null) { // complain if resource couldn't be loaded throw new IllegalArgumentException(uri.toString()); } // sync entry with resource entry = sync(entry, resource); // store entry in cache this.resources.put(uri, entry); } else { if (LOGGER.isDebugEnabled()) { LOGGER.debug("get transformer: cache hit for " + uri); } } if (entry.templates == null) { // create source and templates object (this might trigger uri resolution) Source source = new StreamSource(entry.resource.getInputStream()); source.setSystemId(uri.toString()); entry.templates = getTransformerFactory().newTemplates(source); } return entry.templates.newTransformer(); } catch (Exception e) { throw new TransformerException(e); } } // implementation of 'javax.xml.transform.URIResolver' /** * Called by the processor when it encounters an xsl:include, xsl:import, or * document() function. * * @param href the href attribute, which may be relative or absolute. * @param base the base URI in effect when the href attribute was encountered. * @return a Source object, or null if the href cannot be resolved, and the * processor should try to resolve the URI itself. * @throws TransformerException if an error occurs when trying to resolve the URI. */ public Source resolve(String href, String base) throws TransformerException { try { if (LOGGER.isDebugEnabled()) { LOGGER.debug("resolve: " + href + " against " + base); } // resolve uri URI uri = base != null ? new URI(base).resolve(href) : new URI(href); // lookup cache entry CacheEntry entry = (CacheEntry) this.resources.get(uri); if (entry == null || entry.isDirty()) { if (LOGGER.isDebugEnabled()) { LOGGER.debug("resolve: cache " + (entry == null ? "miss" : "dirty") + " for " + uri); } // load missing/dirty resource Resource resource = load(uri); if (resource == null) { // return null to let the xslt processor attempt to resolve the uri return null; } // sync entry with resource entry = sync(entry, resource); // store entry in cache this.resources.put(uri, entry); if (base != null) { // add dependency to parent entry CacheEntry parent = (CacheEntry) this.resources.get(new URI(base)); parent.dependencies.add(entry); } } else { if (LOGGER.isDebugEnabled()) { LOGGER.debug("resolve: cache hit for " + uri); } } // create source Source source = entry.resource.getSource(); source.setSystemId(uri.toString()); return source; } catch (Exception e) { throw new TransformerException(e); } } // stylesheet loader /** * Adds a resource resolver. * * @param resolver the resource resolver to be added. */ public void addResourceResolver(ResourceResolver resolver) { this.resolvers.add(resolver); } /** * Removes a resource resolver. * * @param resolver the resource resolver to be removed. */ public void removeResourceResolver(ResourceResolver resolver) { this.resolvers.remove(resolver); } // helper private Resource load(URI uri) throws XFormsException { // todo: use connectors some day ? Resource resource; ResourceResolver resolver; for (int i = 0; i < this.resolvers.size(); i++) { resolver = (ResourceResolver) this.resolvers.get(i); resource = resolver.resolve(uri); if (resource != null) { return resource; } } return null; } private CacheEntry sync(CacheEntry entry, Resource resource) { if (entry == null) { // create entry entry = new CacheEntry(resource.lastModified(), resource); } else { // reset entry for reuse entry.lastModified = resource.lastModified(); entry.resource = resource; entry.templates = null; entry.dependencies.clear(); } return entry; } private static class CacheEntry { long lastModified; Resource resource; Templates templates; List dependencies; CacheEntry(long lastModified, Resource resource) { this.lastModified = lastModified; this.resource = resource; this.dependencies = new ArrayList(); } boolean isDirty() { if (this.lastModified < this.resource.lastModified()) { return true; } for (int i = 0; i < this.dependencies.size(); i++) { if (((CacheEntry) this.dependencies.get(i)).isDirty()) { return true; } } return false; } } }