Java tutorial
/* * Copyright (C) 2009, Constantine Plotnikov <constantine.plotnikov@gmail.com> * Copyright (C) 2007, Dave Watson <dwatson@mimvista.com> * Copyright (C) 2009, Google Inc. * Copyright (C) 2009, JetBrains s.r.o. * Copyright (C) 2008-2009, Robin Rosenberg <robin.rosenberg@dewire.com> * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org> * Copyright (C) 2008, Thad Hughes <thadh@thad.corp.google.com> * and other copyright owners as documented in the project's IP log. * * This program and the accompanying materials are made available * under the terms of the Eclipse Distribution License v1.0 which * accompanies this distribution, is reproduced below, and is * available at http://www.eclipse.org/org/documents/edl-v10.php * * All rights reserved. * * Redistribution and use in source and binary forms, with or * without modification, are permitted provided that the following * conditions are met: * * - Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * - Redistributions in binary form must reproduce the above * copyright notice, this list of conditions and the following * disclaimer in the documentation and/or other materials provided * with the distribution. * * - Neither the name of the Eclipse Foundation, Inc. nor the * names of its contributors may be used to endorse or promote * products derived from this software without specific prior * written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ package org.eclipse.jgit.storage.file; import static java.nio.charset.StandardCharsets.UTF_8; import java.io.ByteArrayOutputStream; import java.io.File; import java.io.FileNotFoundException; import java.io.IOException; import java.text.MessageFormat; import org.eclipse.jgit.errors.ConfigInvalidException; import org.eclipse.jgit.errors.LockFailedException; import org.eclipse.jgit.internal.JGitText; import org.eclipse.jgit.internal.storage.file.FileSnapshot; import org.eclipse.jgit.internal.storage.file.LockFile; import org.eclipse.jgit.lib.Config; import org.eclipse.jgit.lib.Constants; import org.eclipse.jgit.lib.ObjectId; import org.eclipse.jgit.lib.StoredConfig; import org.eclipse.jgit.util.FS; import org.eclipse.jgit.util.FileUtils; import org.eclipse.jgit.util.IO; import org.eclipse.jgit.util.RawParseUtils; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * The configuration file that is stored in the file of the file system. */ public class FileBasedConfig extends StoredConfig { private final static Logger LOG = LoggerFactory.getLogger(FileBasedConfig.class); private final File configFile; private final FS fs; private boolean utf8Bom; private volatile FileSnapshot snapshot; private volatile ObjectId hash; /** * Create a configuration with no default fallback. * * @param cfgLocation * the location of the configuration file on the file system * @param fs * the file system abstraction which will be necessary to perform * certain file system operations. */ public FileBasedConfig(File cfgLocation, FS fs) { this(null, cfgLocation, fs); } /** * The constructor * * @param base * the base configuration file * @param cfgLocation * the location of the configuration file on the file system * @param fs * the file system abstraction which will be necessary to perform * certain file system operations. */ public FileBasedConfig(Config base, File cfgLocation, FS fs) { super(base); configFile = cfgLocation; this.fs = fs; this.snapshot = FileSnapshot.DIRTY; this.hash = ObjectId.zeroId(); } /** {@inheritDoc} */ @Override protected boolean notifyUponTransientChanges() { // we will notify listeners upon save() return false; } /** * Get location of the configuration file on disk * * @return location of the configuration file on disk */ public final File getFile() { return configFile; } /** * {@inheritDoc} * <p> * Load the configuration as a Git text style configuration file. * <p> * If the file does not exist, this configuration is cleared, and thus * behaves the same as though the file exists, but is empty. */ @Override public void load() throws IOException, ConfigInvalidException { final int maxRetries = 5; int retryDelayMillis = 20; int retries = 0; while (true) { final FileSnapshot oldSnapshot = snapshot; final FileSnapshot newSnapshot; // don't use config in this snapshot to avoid endless recursion newSnapshot = FileSnapshot.saveNoConfig(getFile()); try { final byte[] in = IO.readFully(getFile()); final ObjectId newHash = hash(in); if (hash.equals(newHash)) { if (oldSnapshot.equals(newSnapshot)) { oldSnapshot.setClean(newSnapshot); } else { snapshot = newSnapshot; } } else { final String decoded; if (isUtf8(in)) { decoded = RawParseUtils.decode(UTF_8, in, 3, in.length); utf8Bom = true; } else { decoded = RawParseUtils.decode(in); } fromText(decoded); snapshot = newSnapshot; hash = newHash; } return; } catch (FileNotFoundException noFile) { // might be locked by another process (see exception Javadoc) if (retries < maxRetries && configFile.exists()) { if (LOG.isDebugEnabled()) { LOG.debug(MessageFormat.format(JGitText.get().configHandleMayBeLocked, Integer.valueOf(retries)), noFile); } try { Thread.sleep(retryDelayMillis); } catch (InterruptedException e) { Thread.currentThread().interrupt(); } retries++; retryDelayMillis *= 2; // max wait 1260 ms continue; } if (configFile.exists()) { throw noFile; } clear(); snapshot = newSnapshot; return; } catch (IOException e) { if (FileUtils.isStaleFileHandle(e) && retries < maxRetries) { if (LOG.isDebugEnabled()) { LOG.debug( MessageFormat.format(JGitText.get().configHandleIsStale, Integer.valueOf(retries)), e); } retries++; continue; } throw new IOException(MessageFormat.format(JGitText.get().cannotReadFile, getFile()), e); } catch (ConfigInvalidException e) { throw new ConfigInvalidException(MessageFormat.format(JGitText.get().cannotReadFile, getFile()), e); } } } /** * {@inheritDoc} * <p> * Save the configuration as a Git text style configuration file. * <p> * <b>Warning:</b> Although this method uses the traditional Git file * locking approach to protect against concurrent writes of the * configuration file, it does not ensure that the file has not been * modified since the last read, which means updates performed by other * objects accessing the same backing file may be lost. */ @Override public void save() throws IOException { final byte[] out; final String text = toText(); if (utf8Bom) { final ByteArrayOutputStream bos = new ByteArrayOutputStream(); bos.write(0xEF); bos.write(0xBB); bos.write(0xBF); bos.write(text.getBytes(UTF_8)); out = bos.toByteArray(); } else { out = Constants.encode(text); } final LockFile lf = new LockFile(getFile()); if (!lf.lock()) throw new LockFailedException(getFile()); try { lf.setNeedSnapshot(true); lf.write(out); if (!lf.commit()) throw new IOException(MessageFormat.format(JGitText.get().cannotCommitWriteTo, getFile())); } finally { lf.unlock(); } snapshot = lf.getCommitSnapshot(); hash = hash(out); // notify the listeners fireConfigChangedEvent(); } /** {@inheritDoc} */ @Override public void clear() { hash = hash(new byte[0]); super.clear(); } private static ObjectId hash(byte[] rawText) { return ObjectId.fromRaw(Constants.newMessageDigest().digest(rawText)); } /** {@inheritDoc} */ @SuppressWarnings("nls") @Override public String toString() { return getClass().getSimpleName() + "[" + getFile().getPath() + "]"; } /** * Whether the currently loaded configuration file is outdated * * @return returns true if the currently loaded configuration file is older * than the file on disk */ public boolean isOutdated() { return snapshot.isModified(getFile()); } /** * {@inheritDoc} * * @since 4.10 */ @Override protected byte[] readIncludedConfig(String relPath) throws ConfigInvalidException { final File file; if (relPath.startsWith("~/")) { //$NON-NLS-1$ file = fs.resolve(fs.userHome(), relPath.substring(2)); } else { file = fs.resolve(configFile.getParentFile(), relPath); } if (!file.exists()) { return null; } try { return IO.readFully(file); } catch (IOException ioe) { throw new ConfigInvalidException(MessageFormat.format(JGitText.get().cannotReadFile, relPath), ioe); } } }