Java tutorial
package org.apache.velocity.tools.view; /* * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, * software distributed under the License is distributed on an * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY * KIND, either express or implied. See the License for the * specific language governing permissions and limitations * under the License. */ import java.io.File; import java.io.InputStream; import java.util.HashMap; import javax.servlet.ServletContext; import org.apache.commons.collections.ExtendedProperties; import org.apache.velocity.exception.ResourceNotFoundException; import org.apache.velocity.runtime.resource.Resource; import org.apache.velocity.runtime.resource.loader.ResourceLoader; /** * Resource loader that uses the ServletContext of a webapp to * load Velocity templates. (it's much easier to use with servlets than * the standard FileResourceLoader, in particular the use of war files * is transparent). * * The default search path is '/' (relative to the webapp root), but * you can change this behaviour by specifying one or more paths * by mean of as many webapp.resource.loader.path properties as needed * in the velocity.properties file. * * All paths must be relative to the root of the webapp. * * To enable caching and cache refreshing the webapp.resource.loader.cache and * webapp.resource.loader.modificationCheckInterval properties need to be * set in the velocity.properties file ... auto-reloading of global macros * requires the webapp.resource.loader.cache property to be set to 'false'. * * @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a> * @author Nathan Bubna * @author <a href="mailto:claude@savoirweb.com">Claude Brisson</a> * @version $Id: WebappResourceLoader.java 712011 2008-11-06 23:35:43Z nbubna $ */ public class WebappResourceLoader extends ResourceLoader { /** The root paths for templates (relative to webapp's root). */ protected String[] paths = null; protected HashMap templatePaths = null; protected ServletContext servletContext = null; /** * This is abstract in the base class, so we need it. * <br> * NOTE: this expects that the ServletContext has already * been placed in the runtime's application attributes * under its full class name (i.e. "javax.servlet.ServletContext"). * * @param configuration the {@link ExtendedProperties} associated with * this resource loader. */ public void init(ExtendedProperties configuration) { log.trace("WebappResourceLoader: initialization starting."); /* get configured paths */ paths = configuration.getStringArray("path"); if (paths == null || paths.length == 0) { paths = new String[1]; paths[0] = "/"; } else { /* make sure the paths end with a '/' */ for (int i = 0; i < paths.length; i++) { if (!paths[i].endsWith("/")) { paths[i] += '/'; } log.info("WebappResourceLoader: added template path - '" + paths[i] + "'"); } } /* get the ServletContext */ Object obj = rsvc.getApplicationAttribute(ServletContext.class.getName()); if (obj instanceof ServletContext) { servletContext = (ServletContext) obj; } else { log.error("WebappResourceLoader: unable to retrieve ServletContext"); } /* init the template paths map */ templatePaths = new HashMap(); log.trace("WebappResourceLoader: initialization complete."); } /** * Get an InputStream so that the Runtime can build a * template with it. * * @param name name of template to get * @return InputStream containing the template * @throws ResourceNotFoundException if template not found * in classpath. */ public synchronized InputStream getResourceStream(String name) throws ResourceNotFoundException { InputStream result = null; if (name == null || name.length() == 0) { throw new ResourceNotFoundException("WebappResourceLoader: No template name provided"); } /* since the paths always ends in '/', * make sure the name never starts with one */ while (name.startsWith("/")) { name = name.substring(1); } Exception exception = null; for (int i = 0; i < paths.length; i++) { String path = paths[i] + name; try { result = servletContext.getResourceAsStream(path); /* save the path and exit the loop if we found the template */ if (result != null) { templatePaths.put(name, paths[i]); break; } } catch (NullPointerException npe) { /* no servletContext was set, whine about it! */ throw npe; } catch (Exception e) { /* only save the first one for later throwing */ if (exception == null) { if (log.isDebugEnabled()) { log.debug("WebappResourceLoader: Could not load " + path, e); } exception = e; } } } /* if we never found the template */ if (result == null) { String msg = "WebappResourceLoader: Resource '" + name + "' not found."; /* convert to a general Velocity ResourceNotFoundException */ if (exception == null) { throw new ResourceNotFoundException(msg); } else { msg += " Due to: " + exception; throw new ResourceNotFoundException(msg, exception); } } return result; } private File getCachedFile(String rootPath, String fileName) { // we do this when we cache a resource, // so do it again to ensure a match while (fileName.startsWith("/")) { fileName = fileName.substring(1); } String savedPath = (String) templatePaths.get(fileName); return new File(rootPath + savedPath, fileName); } /** * Checks to see if a resource has been deleted, moved or modified. * * @param resource Resource The resource to check for modification * @return boolean True if the resource has been modified */ public boolean isSourceModified(Resource resource) { String rootPath = servletContext.getRealPath("/"); if (rootPath == null) { // rootPath is null if the servlet container cannot translate the // virtual path to a real path for any reason (such as when the // content is being made available from a .war archive) return false; } // first, try getting the previously found file String fileName = resource.getName(); File cachedFile = getCachedFile(rootPath, fileName); if (!cachedFile.exists()) { /* then the source has been moved and/or deleted */ return true; } /* check to see if the file can now be found elsewhere * before it is found in the previously saved path */ File currentFile = null; for (int i = 0; i < paths.length; i++) { currentFile = new File(rootPath + paths[i], fileName); if (currentFile.canRead()) { /* stop at the first resource found * (just like in getResourceStream()) */ break; } } /* if the current is the cached and it is readable */ if (cachedFile.equals(currentFile) && cachedFile.canRead()) { /* then (and only then) do we compare the last modified values */ return (cachedFile.lastModified() != resource.getLastModified()); } else { /* we found a new file for the resource * or the resource is no longer readable. */ return true; } } /** * Checks to see when a resource was last modified * * @param resource Resource the resource to check * @return long The time when the resource was last modified or 0 if the file can't be read */ public long getLastModified(Resource resource) { String rootPath = servletContext.getRealPath("/"); if (rootPath == null) { // rootPath is null if the servlet container cannot translate the // virtual path to a real path for any reason (such as when the // content is being made available from a .war archive) return 0; } File cachedFile = getCachedFile(rootPath, resource.getName()); if (cachedFile.canRead()) { return cachedFile.lastModified(); } else { return 0; } } }