Java tutorial
/* The contents of this file are subject to the license and copyright terms * detailed in the license directory at the root of the source tree (also * available online at http://fedora-commons.org/license/). */ package org.fcrepo.localservices.saxon; import java.io.IOException; import java.io.InputStream; import java.net.MalformedURLException; import java.net.URL; import java.util.Enumeration; import java.util.HashMap; import java.util.Iterator; import java.util.Map; import javax.servlet.ServletConfig; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.xml.transform.OutputKeys; import javax.xml.transform.Templates; import javax.xml.transform.Transformer; import javax.xml.transform.TransformerException; import javax.xml.transform.TransformerFactory; import javax.xml.transform.stream.StreamResult; import javax.xml.transform.stream.StreamSource; import net.sf.saxon.FeatureKeys; import net.sf.saxon.value.StringValue; import org.apache.commons.httpclient.HttpClient; import org.apache.commons.httpclient.MultiThreadedHttpConnectionManager; import org.apache.commons.httpclient.UsernamePasswordCredentials; import org.apache.commons.httpclient.auth.AuthScope; import org.apache.commons.httpclient.methods.GetMethod; /** * A service that transforms a supplied input document using a supplied * stylesheet, with stylesheet caching. Adapted from the SaxonServlet.java * example file contained in the source distribution of "The SAXON XSLT * Processor from Michael Kay". * * <pre> * ----------------------------------------------------------------------------- * The original code is Copyright © 2001 by Michael Kay. All rights * reserved. The current project homepage for Saxon may be found at: * <a href="http://saxon.sourceforge.net/">http://saxon.sourceforge.net/</a>. * * Portions created for the Fedora Repository System are Copyright © 2002-2007 * by The Rector and Visitors of the University of Virginia and Cornell * University. All rights reserved. * ----------------------------------------------------------------------------- * </pre> * * @author Michael Kay * @author Ross Wayland * @author Chris Wilper * @version $Id$ */ public class SaxonServlet extends HttpServlet { private static final long serialVersionUID = 2L; /** time to wait for getting data via http before giving up */ public final int TIMEOUT_SECONDS = 10; /** start string for a servlet config parameter name that gives creds */ private final String CRED_PARAM_START = "credentials for "; /** urlString-to-Templates map of cached stylesheets */ private Map<String, Templates> m_cache; /** pathString-to-Credentials map of configured credentials */ private Map<String, UsernamePasswordCredentials> m_creds; /** provider of http connections */ private MultiThreadedHttpConnectionManager m_cManager; /** * Initialize the servlet by setting up the stylesheet cache, the http * connection manager, and configuring credentials for the http client. */ @Override public void init(ServletConfig config) throws ServletException { m_cache = new HashMap<String, Templates>(); m_creds = new HashMap<String, UsernamePasswordCredentials>(); m_cManager = new MultiThreadedHttpConnectionManager(); m_cManager.getParams().setConnectionTimeout(TIMEOUT_SECONDS * 1000); Enumeration<?> enm = config.getInitParameterNames(); while (enm.hasMoreElements()) { String name = (String) enm.nextElement(); if (name.startsWith(CRED_PARAM_START)) { String value = config.getInitParameter(name); if (value.indexOf(":") == -1) { throw new ServletException( "Malformed credentials for " + name + " -- expected ':' user/pass delimiter"); } String[] parts = value.split(":"); String user = parts[0]; StringBuffer pass = new StringBuffer(); for (int i = 1; i < parts.length; i++) { if (i > 1) { pass.append(':'); } pass.append(parts[i]); } m_creds.put(name.substring(CRED_PARAM_START.length()), new UsernamePasswordCredentials(user, pass.toString())); } } } /** * Accept a GET request and produce a response. HTTP Request Parameters: * <ul> * <li>source - URL of source document</li> * <li>style - URL of stylesheet</li> * <li>clear-stylesheet-cache - if set to yes, empties the cache before * running. * </ul> * * @param req * The HTTP request * @param res * The HTTP response */ @Override public void doGet(HttpServletRequest req, HttpServletResponse res) throws IOException { String source = req.getParameter("source"); String style = req.getParameter("style"); String clear = req.getParameter("clear-stylesheet-cache"); if (clear != null && clear.equals("yes")) { synchronized (m_cache) { m_cache = new HashMap<String, Templates>(); } } try { apply(style, source, req, res); } catch (Exception e) { res.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, e.getMessage()); e.printStackTrace(); } } /** * Accept an POST request and produce a response (same behavior as GET). */ @Override public void doPost(HttpServletRequest req, HttpServletResponse res) throws IOException { doGet(req, res); } @Override public String getServletInfo() { return "Calls SAXON to apply a stylesheet to a source document"; } /** * Apply stylesheet to source document */ private void apply(String style, String source, HttpServletRequest req, HttpServletResponse res) throws Exception { // Validate parameters if (style == null) { throw new TransformerException("No style parameter supplied"); } if (source == null) { throw new TransformerException("No source parameter supplied"); } InputStream sourceStream = null; try { // Load the stylesheet (adding to cache if necessary) Templates pss = tryCache(style); Transformer transformer = pss.newTransformer(); Enumeration<?> p = req.getParameterNames(); while (p.hasMoreElements()) { String name = (String) p.nextElement(); if (!(name.equals("style") || name.equals("source"))) { String value = req.getParameter(name); transformer.setParameter(name, new StringValue(value)); } } // Start loading the document to be transformed sourceStream = getInputStream(source); // Set the appropriate output mime type String mime = pss.getOutputProperties().getProperty(OutputKeys.MEDIA_TYPE); if (mime == null) { res.setContentType("text/html"); } else { res.setContentType(mime); } // Transform StreamSource ss = new StreamSource(sourceStream); ss.setSystemId(source); transformer.transform(ss, new StreamResult(res.getOutputStream())); } finally { if (sourceStream != null) { try { sourceStream.close(); } catch (Exception e) { } } } } /** * Maintain prepared stylesheets in memory for reuse */ private Templates tryCache(String url) throws Exception { Templates x = (Templates) m_cache.get(url); if (x == null) { synchronized (m_cache) { if (!m_cache.containsKey(url)) { TransformerFactory factory = TransformerFactory.newInstance(); if (factory.getClass().getName().equals("net.sf.saxon.TransformerFactoryImpl")) { factory.setAttribute(FeatureKeys.VERSION_WARNING, Boolean.FALSE); } StreamSource ss = new StreamSource(getInputStream(url)); ss.setSystemId(url); x = factory.newTemplates(ss); m_cache.put(url, x); } } } return x; } /** * Get the content at the given location using the configured credentials * (if any). */ private InputStream getInputStream(String url) throws Exception { GetMethod getMethod = new GetMethod(url); HttpClient client = new HttpClient(m_cManager); UsernamePasswordCredentials creds = getCreds(url); if (creds != null) { client.getState().setCredentials(AuthScope.ANY, creds); client.getParams().setAuthenticationPreemptive(true); getMethod.setDoAuthentication(true); } getMethod.setFollowRedirects(true); HttpInputStream in = new HttpInputStream(client, getMethod, url); if (in.getStatusCode() != 200) { try { in.close(); } catch (Exception e) { } throw new IOException("HTTP request failed. Got status code " + in.getStatusCode() + " from remote server while attempting to GET " + url); } else { return in; } } /** * Return the credentials for the realmPath that most closely matches the * given url, or null if none found. */ private UsernamePasswordCredentials getCreds(String url) throws Exception { url = normalizeURL(url); url = url.substring(url.indexOf("/") + 2); UsernamePasswordCredentials longestMatch = null; int longestMatchLength = 0; Iterator<String> iter = m_creds.keySet().iterator(); while (iter.hasNext()) { String realmPath = (String) iter.next(); if (url.startsWith(realmPath)) { int matchLength = realmPath.length(); if (matchLength > longestMatchLength) { longestMatchLength = matchLength; longestMatch = (UsernamePasswordCredentials) m_creds.get(realmPath); } } } return longestMatch; } /** * Return a URL string in which the port is always specified. */ private static String normalizeURL(String urlString) throws MalformedURLException { URL url = new URL(urlString); if (url.getPort() == -1) { return url.getProtocol() + "://" + url.getHost() + ":" + url.getDefaultPort() + url.getFile() + (url.getRef() != null ? "#" + url.getRef() : ""); } else { return urlString; } } }