Java tutorial
package com.sri.vt.majic.util.clean; /* * 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 org.apache.maven.plugin.logging.Log; import org.codehaus.plexus.util.Os; import java.io.File; import java.io.IOException; /** * Cleans directories. * * @author Benjamin Bentmann * * SRI Notes: This is the Cleaner class from the maven-clean-plugin with three changes. * 1. Made the class public * 2. Added verbose logging when retrying delete on Windows. * 3. Test symbolic links with new Java 7 API instead of guessing via checking if canonical. */ public class Cleaner { private static final boolean ON_WINDOWS = Os.isFamily(Os.FAMILY_WINDOWS); private final Logger logDebug; private final Logger logInfo; private final Logger logVerbose; private final Logger logWarn; /** * Creates a new cleaner. * * @param log The logger to use, may be <code>null</code> to disable logging. * @param verbose Whether to perform verbose logging. */ public Cleaner(final Log log, boolean verbose) { logDebug = (log == null || !log.isDebugEnabled()) ? null : new Logger() { public void log(CharSequence message) { log.debug(message); } }; logInfo = (log == null || !log.isInfoEnabled()) ? null : new Logger() { public void log(CharSequence message) { log.info(message); } }; logWarn = (log == null || !log.isWarnEnabled()) ? null : new Logger() { public void log(CharSequence message) { log.warn(message); } }; logVerbose = verbose ? logInfo : logDebug; } /** * Deletes the specified directories and its contents. * * @param basedir The directory to delete, must not be <code>null</code>. Non-existing directories will be silently * ignored. * @param selector The selector used to determine what contents to delete, may be <code>null</code> to delete * everything. * @param followSymlinks Whether to follow symlinks. * @param failOnError Whether to abort with an exception in case a selected file/directory could not be deleted. * @param retryOnError Whether to undertake additional delete attempts in case the first attempt failed. * @throws IOException If a file/directory could not be deleted and <code>failOnError</code> is <code>true</code>. */ public void delete(File basedir, Selector selector, boolean followSymlinks, boolean failOnError, boolean retryOnError) throws IOException { if (!basedir.isDirectory()) { if (!basedir.exists()) { if (logDebug != null) { logDebug.log("Skipping non-existing directory " + basedir); } return; } throw new IOException("Invalid base directory " + basedir); } if (logInfo != null) { logInfo.log("Deleting " + basedir + (selector != null ? " (" + selector + ")" : "")); } File file = followSymlinks ? basedir : basedir.getCanonicalFile(); delete(file, "", selector, followSymlinks, failOnError, retryOnError); } /** * Deletes the specified file or directory. * * @param file The file/directory to delete, must not be <code>null</code>. * @param pathname The relative pathname of the file, using {@link File#separatorChar}, must not be * <code>null</code>. * @param selector The selector used to determine what contents to delete, may be <code>null</code> to delete * everything. * @param followSymlinks Whether to follow symlinks. * @param failOnError Whether to abort with an exception in case a selected file/directory could not be deleted. * @param retryOnError Whether to undertake additional delete attempts in case the first attempt failed. * @return The result of the cleaning, never <code>null</code>. * @throws IOException If a file/directory could not be deleted and <code>failOnError</code> is <code>true</code>. */ private Result delete(File file, String pathname, Selector selector, boolean followSymlinks, boolean failOnError, boolean retryOnError) throws IOException { Result result = new Result(); boolean isDirectory = file.isDirectory(); if (isDirectory) { if (selector == null || selector.couldHoldSelected(pathname)) { if (followSymlinks || !java.nio.file.Files.isSymbolicLink(file.toPath())) { String[] filenames = file.list(); if (filenames != null) { String prefix = (pathname.length() > 0) ? pathname + File.separatorChar : ""; for (int i = filenames.length - 1; i >= 0; i--) { String filename = filenames[i]; File child = new File(file, filename); result.update(delete(child, prefix + filename, selector, followSymlinks, failOnError, retryOnError)); } } } else if (logDebug != null) { logDebug.log("Not recursing into symlink " + file); } } else if (logDebug != null) { logDebug.log("Not recursing into directory without included files " + file); } } if (!result.excluded && (selector == null || selector.isSelected(pathname))) { if (logVerbose != null) { if (isDirectory) { logVerbose.log("Deleting directory " + file); } else if (file.exists()) { logVerbose.log("Deleting file " + file); } else { logVerbose.log("Deleting dangling symlink " + file); } } result.failures += delete(file, failOnError, retryOnError); } else { result.excluded = true; } return result; } /** * Deletes the specified file, directory. If the path denotes a symlink, only the link is removed, its target is * left untouched. * * @param file The file/directory to delete, must not be <code>null</code>. * @param failOnError Whether to abort with an exception in case the file/directory could not be deleted. * @param retryOnError Whether to undertake additional delete attempts in case the first attempt failed. * @return <code>0</code> if the file was deleted, <code>1</code> otherwise. * @throws IOException If a file/directory could not be deleted and <code>failOnError</code> is <code>true</code>. */ private int delete(File file, boolean failOnError, boolean retryOnError) throws IOException { if (!file.delete()) { boolean deleted = false; if (retryOnError) { if (ON_WINDOWS) { // try to release any locks held by non-closed files System.gc(); } int[] delays = { 50, 250, 750, 1500, 5000 }; for (int i = 0; !deleted && i < delays.length; i++) { try { if (logWarn != null) { logWarn.log("Delete of " + file + " failed, trying again in " + delays[i] + " milliseconds"); } Thread.sleep(delays[i]); } catch (InterruptedException e) { // ignore } deleted = file.delete() || !file.exists(); } } else { deleted = !file.exists(); } if (!deleted) { if (failOnError) { throw new IOException("Failed to delete " + file); } else { if (logWarn != null) { logWarn.log("Failed to delete " + file); } return 1; } } } return 0; } private static class Result { public int failures; public boolean excluded; public void update(Result result) { failures += result.failures; excluded |= result.excluded; } } private static interface Logger { public void log(CharSequence message); } }