Java tutorial
/* * 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. */ /* * $Id: SystemIDResolver.java 468655 2006-10-28 07:12:06Z minchau $ */ import java.io.File; import java.net.URI; import javax.xml.transform.TransformerException; /** * This class is used to resolve relative URIs and SystemID * strings into absolute URIs. * * <p>This is a generic utility for resolving URIs, other than the * fact that it's declared to throw TransformerException. Please * see code comments for details on how resolution is performed.</p> * @xsl.usage internal */ public class SystemIDResolver { /** * Get an absolute URI from a given relative URI (local path). * * <p>The relative URI is a local filesystem path. The path can be * absolute or relative. If it is a relative path, it is resolved relative * to the system property "user.dir" if it is available; if not (i.e. in an * Applet perhaps which throws SecurityException) then we just return the * relative path. The space and backslash characters are also replaced to * generate a good absolute URI.</p> * * @param localPath The relative URI to resolve * * @return Resolved absolute URI */ public static String getAbsoluteURIFromRelative(String localPath) { if (localPath == null || localPath.length() == 0) return ""; // If the local path is a relative path, then it is resolved against // the "user.dir" system property. String absolutePath = localPath; if (!isAbsolutePath(localPath)) { try { absolutePath = getAbsolutePathFromRelativePath(localPath); } // user.dir not accessible from applet catch (SecurityException se) { return "file:" + localPath; } } String urlString; if (null != absolutePath) { if (absolutePath.startsWith(File.separator)) urlString = "file://" + absolutePath; else urlString = "file:///" + absolutePath; } else urlString = "file:" + localPath; return replaceChars(urlString); } /** * Return an absolute path from a relative path. * * @param relativePath A relative path * @return The absolute path */ private static String getAbsolutePathFromRelativePath(String relativePath) { return new File(relativePath).getAbsolutePath(); } /** * Return true if the systemId denotes an absolute URI . * * @param systemId The systemId string * @return true if the systemId is an an absolute URI */ public static boolean isAbsoluteURI(String systemId) { /** http://www.ietf.org/rfc/rfc2396.txt * Authors should be aware that a path segment which contains a colon * character cannot be used as the first segment of a relative URI path * (e.g., "this:that"), because it would be mistaken for a scheme name. **/ /** * %REVIEW% Can we assume here that systemId is a valid URI? * It looks like we cannot ( See discussion of this common problem in * Bugzilla Bug 22777 ). **/ //"fix" for Bugzilla Bug 22777 if (isWindowsAbsolutePath(systemId)) { return false; } final int fragmentIndex = systemId.indexOf('#'); final int queryIndex = systemId.indexOf('?'); final int slashIndex = systemId.indexOf('/'); final int colonIndex = systemId.indexOf(':'); //finding substring before '#', '?', and '/' int index = systemId.length() - 1; if (fragmentIndex > 0) index = fragmentIndex; if ((queryIndex > 0) && (queryIndex < index)) index = queryIndex; if ((slashIndex > 0) && (slashIndex < index)) index = slashIndex; // return true if there is ':' before '#', '?', and '/' return ((colonIndex > 0) && (colonIndex < index)); } /** * Return true if the local path is an absolute path. * * @param systemId The path string * @return true if the path is absolute */ public static boolean isAbsolutePath(String systemId) { if (systemId == null) return false; final File file = new File(systemId); return file.isAbsolute(); } /** * Return true if the local path is a Windows absolute path. * * @param systemId The path string * @return true if the path is a Windows absolute path */ private static boolean isWindowsAbsolutePath(String systemId) { if (!isAbsolutePath(systemId)) return false; // On Windows, an absolute path starts with "[drive_letter]:\". if (systemId.length() > 2 && systemId.charAt(1) == ':' && Character.isLetter(systemId.charAt(0)) && (systemId.charAt(2) == '\\' || systemId.charAt(2) == '/')) return true; else return false; } /** * Replace spaces with "%20" and backslashes with forward slashes in * the input string to generate a well-formed URI string. * * @param str The input string * @return The string after conversion */ private static String replaceChars(String str) { StringBuffer buf = new StringBuffer(str); int length = buf.length(); for (int i = 0; i < length; i++) { char currentChar = buf.charAt(i); // Replace space with "%20" if (currentChar == ' ') { buf.setCharAt(i, '%'); buf.insert(i + 1, "20"); length = length + 2; i = i + 2; } // Replace backslash with forward slash else if (currentChar == '\\') { buf.setCharAt(i, '/'); } } return buf.toString(); } /** * Take a SystemID string and try to turn it into a good absolute URI. * * @param systemId A URI string, which may be absolute or relative. * * @return The resolved absolute URI */ public static String getAbsoluteURI(String systemId) { String absoluteURI = systemId; if (isAbsoluteURI(systemId)) { // Only process the systemId if it starts with "file:". if (systemId.startsWith("file:")) { String str = systemId.substring(5); // Resolve the absolute path if the systemId starts with "file:///" // or "file:/". Don't do anything if it only starts with "file://". if (str != null && str.startsWith("/")) { if (str.startsWith("///") || !str.startsWith("//")) { // A Windows path containing a drive letter can be relative. // A Unix path starting with "file:/" is always absolute. int secondColonIndex = systemId.indexOf(':', 5); if (secondColonIndex > 0) { String localPath = systemId.substring(secondColonIndex - 1); try { if (!isAbsolutePath(localPath)) absoluteURI = systemId.substring(0, secondColonIndex - 1) + getAbsolutePathFromRelativePath(localPath); } catch (SecurityException se) { return systemId; } } } } else { return getAbsoluteURIFromRelative(systemId.substring(5)); } return replaceChars(absoluteURI); } else return systemId; } else return getAbsoluteURIFromRelative(systemId); } }