Java tutorial
package org.apache.flex.forks.velocity.runtime.resource.loader; /* * Copyright 2001,2004 The Apache Software Foundation. * * Licensed 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.io.FileInputStream; import java.io.BufferedInputStream; import java.io.FileNotFoundException; import java.util.Hashtable; import java.util.Vector; import org.apache.flex.forks.velocity.util.StringUtils; import org.apache.flex.forks.velocity.runtime.resource.Resource; import org.apache.flex.forks.velocity.exception.ResourceNotFoundException; import org.apache.commons.collections.ExtendedProperties; /** * A loader for templates stored on the file system. * * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a> * @version $Id: FileResourceLoader.java,v 1.19.4.1 2004/03/03 23:23:02 geirm Exp $ */ public class FileResourceLoader extends ResourceLoader { /** * The paths to search for templates. */ private Vector paths = null; /** * Used to map the path that a template was found on * so that we can properly check the modification * times of the files. */ private Hashtable templatePaths = new Hashtable(); public void init(ExtendedProperties configuration) { rsvc.info("FileResourceLoader : initialization starting."); paths = configuration.getVector("path"); /* * lets tell people what paths we will be using */ int sz = paths.size(); for (int i = 0; i < sz; i++) { rsvc.info("FileResourceLoader : adding path '" + (String) paths.get(i) + "'"); } rsvc.info("FileResourceLoader : 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 the file template path. */ public synchronized InputStream getResourceStream(String templateName) throws ResourceNotFoundException { /* * Make sure we have a valid templateName. */ if (templateName == null || templateName.length() == 0) { /* * If we don't get a properly formed templateName then * there's not much we can do. So we'll forget about * trying to search any more paths for the template. */ throw new ResourceNotFoundException("Need to specify a file name or file path!"); } String template = StringUtils.normalizePath(templateName); if (template == null || template.length() == 0) { String msg = "File resource error : argument " + template + " contains .. and may be trying to access " + "content outside of template root. Rejected."; rsvc.error("FileResourceLoader : " + msg); throw new ResourceNotFoundException(msg); } /* * if a / leads off, then just nip that :) */ if (template.startsWith("/")) { template = template.substring(1); } int size = paths.size(); for (int i = 0; i < size; i++) { String path = (String) paths.get(i); InputStream inputStream = findTemplate(path, template); if (inputStream != null) { /* * Store the path that this template came * from so that we can check its modification * time. */ templatePaths.put(templateName, path); return inputStream; } } /* * We have now searched all the paths for * templates and we didn't find anything so * throw an exception. */ String msg = "FileResourceLoader Error: cannot find resource " + template; throw new ResourceNotFoundException(msg); } /** * Try to find a template given a normalized path. * * @param String a normalized path * @return InputStream input stream that will be parsed * */ private InputStream findTemplate(String path, String template) { try { File file = new File(path, template); if (file.canRead()) { return new BufferedInputStream(new FileInputStream(file.getAbsolutePath())); } else { return null; } } catch (FileNotFoundException fnfe) { /* * log and convert to a general Velocity ResourceNotFoundException */ return null; } } /** * How to keep track of all the modified times * across the paths. Note that a file might have * appeared in a directory which is earlier in the * path; so we should search the path and see if * the file we find that way is the same as the one * that we have cached. */ public boolean isSourceModified(Resource resource) { /* * we assume that the file needs to be reloaded; * if we find the original file and it's unchanged, * then we'll flip this. */ boolean modified = true; String fileName = resource.getName(); String path = (String) templatePaths.get(fileName); File currentFile = null; for (int i = 0; currentFile == null && i < paths.size(); i++) { String testPath = (String) paths.get(i); File testFile = new File(testPath, fileName); if (testFile.canRead()) { currentFile = testFile; } } File file = new File(path, fileName); if (currentFile == null || !file.exists()) { /* * noop: if the file is missing now (either the cached * file is gone, or the file can no longer be found) * then we leave modified alone (it's set to true); a * reload attempt will be done, which will either use * a new template or fail with an appropriate message * about how the file couldn't be found. */ } else if (currentFile.equals(file) && file.canRead()) { /* * if only if currentFile is the same as file and * file.lastModified() is the same as * resource.getLastModified(), then we should use the * cached version. */ modified = (file.lastModified() != resource.getLastModified()); } /* * rsvc.debug("isSourceModified for " + fileName + ": " + modified); */ return modified; } public long getLastModified(Resource resource) { String path = (String) templatePaths.get(resource.getName()); File file = new File(path, resource.getName()); if (file.canRead()) { return file.lastModified(); } else { return 0; } } }