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. */ package org.apache.openjpa.lib.util; import java.io.BufferedInputStream; import java.io.BufferedOutputStream; import java.io.BufferedWriter; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.FileWriter; import java.io.IOException; import java.io.OutputStream; import java.io.OutputStreamWriter; import java.io.PrintWriter; import java.io.UnsupportedEncodingException; import java.io.Writer; import java.net.URL; import java.net.URLDecoder; import java.security.AccessController; import java.security.PrivilegedActionException; import org.apache.commons.lang.StringUtils; import org.apache.commons.lang.exception.NestableRuntimeException; import serp.util.Strings; /** * Utility operations on files. * * @author Abe White * @nojavadoc */ public class Files { /** * Backup the given file to a new file called <file-name>~. If * the file does not exist or a backup could not be created, returns null. */ public static File backup(File file, boolean copy) { if (file == null || !(AccessController.doPrivileged(J2DoPrivHelper.existsAction(file))).booleanValue()) return null; // create new file object copy so we don't modify the original String aPath = AccessController.doPrivileged(J2DoPrivHelper.getAbsolutePathAction(file)); File clone = new File(aPath); File bk = new File(aPath + "~"); if (!(AccessController.doPrivileged(J2DoPrivHelper.renameToAction(clone, bk))).booleanValue()) return null; if (copy) { try { copy(bk, file); } catch (IOException ioe) { throw new NestableRuntimeException(ioe); } } return bk; } /** * Revert the given backup file to the original location. If the given * file's name does not end in '~', the '~' is appended before proceeding. * If the backup file does not exist or could not be reverted, returns null. */ public static File revert(File backup, boolean copy) { if (backup == null) return null; if (!backup.getName().endsWith("~")) backup = new File(backup.getPath() + "~"); if (!(AccessController.doPrivileged(J2DoPrivHelper.existsAction(backup))).booleanValue()) return null; // create new file object copy so we don't modify the original String path = AccessController.doPrivileged(J2DoPrivHelper.getAbsolutePathAction(backup)); File clone = new File(path); File orig = new File(path.substring(0, path.length() - 1)); if (!(AccessController.doPrivileged(J2DoPrivHelper.renameToAction(clone, orig))).booleanValue()) return null; if (copy) { try { copy(orig, backup); } catch (IOException ioe) { throw new NestableRuntimeException(ioe); } } return orig; } /** * Return the source file for the given class, or null if the * source is not in the CLASSPATH. */ public static File getSourceFile(Class cls) { return getClassFile(cls, ".java"); } /** * Return the class file of the given class, or null if the * class is in a jar. */ public static File getClassFile(Class cls) { return getClassFile(cls, ".class"); } /** * Return the file for the class resource with the given extension. */ private static File getClassFile(Class cls, String ext) { String name = Strings.getClassName(cls); // if it's an inner class, use the parent class name int innerIdx = name.indexOf('$'); if (innerIdx != -1) name = name.substring(0, innerIdx); URL rsrc = AccessController.doPrivileged(J2DoPrivHelper.getResourceAction(cls, name + ext)); if (rsrc != null && rsrc.getProtocol().equals("file")) return new File(URLDecoder.decode(rsrc.getFile())); return null; } /** * Return the file for the given package. If the given base directory * matches the given package structure, it will be used as-is. If not, * the package structure will be added beneath the base directory. If * the base directory is null, the current working directory will be * used as the base. */ public static File getPackageFile(File base, String pkg, boolean mkdirs) { if (base == null) base = new File(AccessController.doPrivileged(J2DoPrivHelper.getPropertyAction("user.dir"))); if (StringUtils.isEmpty(pkg)) { if (mkdirs && !(AccessController.doPrivileged(J2DoPrivHelper.existsAction(base))).booleanValue()) AccessController.doPrivileged(J2DoPrivHelper.mkdirsAction(base)); return base; } pkg = pkg.replace('.', File.separatorChar); File file = null; try { if ((AccessController.doPrivileged(J2DoPrivHelper.getCanonicalPathAction(base))).endsWith(pkg)) file = base; else file = new File(base, pkg); } catch (PrivilegedActionException pae) { throw new NestableRuntimeException((IOException) pae.getException()); } catch (IOException ioe) { throw new NestableRuntimeException(ioe); } if (mkdirs && !(AccessController.doPrivileged(J2DoPrivHelper.existsAction(file))).booleanValue()) AccessController.doPrivileged(J2DoPrivHelper.mkdirsAction(file)); return file; } /** * Check the given string for a matching file. The string is first * tested to see if it is an existing file path. If it does not * represent an existing file, it is checked as a resource name of a * file. If no resource exists, then it is interpreted as a path * to a file that does not exist yet. * * @param name the file path or resource name * @param loader a class loader to use in resource lookup, or null * to use the thread's context loader */ public static File getFile(String name, ClassLoader loader) { if (name == null) return null; File file = new File(name); if ((AccessController.doPrivileged(J2DoPrivHelper.existsAction(file))).booleanValue()) return file; if (loader == null) loader = AccessController.doPrivileged(J2DoPrivHelper.getContextClassLoaderAction()); URL url = AccessController.doPrivileged(J2DoPrivHelper.getResourceAction(loader, name)); if (url != null) { String urlFile = url.getFile(); if (urlFile != null) { File rsrc = new File(URLDecoder.decode(urlFile)); if ((AccessController.doPrivileged(J2DoPrivHelper.existsAction(rsrc))).booleanValue()) return rsrc; } } // go back to original non-existant file path return file; } /** * Return a writer to the stream(stdout or stderr) or file named by the * given string. * * @see #getFile */ public static Writer getWriter(String file, ClassLoader loader) throws IOException { if (file == null) return null; if ("stdout".equals(file)) return new PrintWriter(System.out); if ("stderr".equals(file)) return new PrintWriter(System.err); try { return new FileWriter(getFile(file, loader)); } catch (IOException ioe) { throw new NestableRuntimeException(ioe); } } /** * Return a writer to the stream(stdout or stderr) or file named by the * given string set to the provided charset encoding. * * @see #getOutputStream */ public static Writer getWriter(String file, ClassLoader loader, String enc) throws IOException { if (file == null) return null; if (enc == null) { // call the non-encoded version of the method return getWriter(file, loader); } try { if ("stdout".equals(file)) return new PrintWriter(new OutputStreamWriter(System.out, enc)); else if ("stderr".equals(file)) return new PrintWriter(new OutputStreamWriter(System.err, enc)); else return new BufferedWriter(new OutputStreamWriter(getOutputStream(file, loader), enc)); } catch (IOException ioe) { throw new NestableRuntimeException(ioe); } } /** * Return an output stream to the stream(stdout or stderr) or file named * by the given string. * * @see #getFile */ public static OutputStream getOutputStream(String file, ClassLoader loader) { if (file == null) return null; if ("stdout".equals(file)) return System.out; if ("stderr".equals(file)) return System.err; try { return AccessController.doPrivileged(J2DoPrivHelper.newFileOutputStreamAction(getFile(file, loader))); } catch (PrivilegedActionException pae) { throw new NestableRuntimeException(pae.getException()); } catch (IOException ioe) { throw new NestableRuntimeException(ioe); } } /** * Copy a file. Return false if <code>from</code> does not exist. */ public static boolean copy(File from, File to) throws IOException { if (from == null || to == null || !(AccessController.doPrivileged(J2DoPrivHelper.existsAction(from))).booleanValue()) return false; FileInputStream in = null; FileOutputStream out = null; try { in = AccessController.doPrivileged(J2DoPrivHelper.newFileInputStreamAction(from)); BufferedInputStream inbuf = new BufferedInputStream(in); out = AccessController.doPrivileged(J2DoPrivHelper.newFileOutputStreamAction(to)); BufferedOutputStream outbuf = new BufferedOutputStream(out); for (int b; (b = inbuf.read()) != -1; outbuf.write(b)) ; outbuf.flush(); return true; } catch (PrivilegedActionException pae) { throw (FileNotFoundException) pae.getException(); } finally { if (in != null) try { in.close(); } catch (Exception e) { } if (out != null) try { out.close(); } catch (Exception e) { } } } }