Java tutorial
/* * Copyright (c) 2012. betterFORM Project - http://www.betterform.de * Licensed under the terms of BSD License */ package de.betterform.xml.xslt.impl; import de.betterform.xml.xforms.exception.XFormsException; import de.betterform.xml.xslt.TransformerService; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; 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 implementation 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 2922 2007-10-17 14:07:48Z lars $ */ public class CachingTransformerService implements TransformerService, URIResolver { private static final Log LOGGER = LogFactory.getLog(CachingTransformerService.class); private HashMap resources; private HashMap<String, URI> name2URI; private ArrayList resolvers; private TransformerFactory transformerFactory; private boolean nocache = false; /** * Creates a new caching transformer service. */ public CachingTransformerService() { this.resources = new HashMap(); this.name2URI = new HashMap<String, URI>(); this.resolvers = new ArrayList(); } /** * Creates a new caching transformer service. * * @param resolver a resource resolver. */ public CachingTransformerService(ResourceResolver resolver) { this(); addResourceResolver(resolver); } // implementation of 'de.betterform.xml.xslt.TransformerService' /** * Returns the transformer factory. * * @return the transformer factory. */ public TransformerFactory getTransformerFactory() { if (this.transformerFactory == null) { this.transformerFactory = new net.sf.saxon.TransformerFactoryImpl(); this.transformerFactory.setURIResolver(this); this.transformerFactory.setErrorListener(new XmlStylesheetTransformerErrorListener()); } return this.transformerFactory; } /** * Sets the transformer factory. * * @param factory the transformer factory. */ public void setTransformerFactory(TransformerFactory factory) throws TransformerException { throw new TransformerException( "You cannot set the TransformerFactory for this implementation. This service uses Saxon as XSLT engine."); } /** * 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(); } public Transformer getTransformerByName(String xsltFileName) throws TransformerException { URI uri = this.name2URI.get(xsltFileName); return getTransformer(uri); } /** * 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 (nocache == true || 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); this.name2URI.put(getXsltName(uri), uri); } 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); } } private String getXsltName(URI uri) { String s = uri.toString(); return s.substring(s.lastIndexOf("/") + 1); } public void setNoCache(boolean b) { this.nocache = b; } // 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 (nocache == true || entry == null || entry.isDirty() || !(entry.isTransform())) { 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; } boolean isTransform() throws XFormsException { //todo: will only work with HttpResource if (this.resource.getSource().getSystemId() != null && this.resource.getSource().getSystemId().endsWith(".xsl")) { return true; } else { return false; } } } private static class XmlStylesheetTransformerErrorListener implements javax.xml.transform.ErrorListener { public void error(javax.xml.transform.TransformerException ex) throws javax.xml.transform.TransformerException { ex.printStackTrace(); throw ex; } public void fatalError(javax.xml.transform.TransformerException ex) throws javax.xml.transform.TransformerException { ex.printStackTrace(); throw ex; } public void warning(javax.xml.transform.TransformerException ex) throws javax.xml.transform.TransformerException { ex.printStackTrace(); throw ex; } } }