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 com.datos.vfs.provider.tar; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; import java.util.ArrayList; import java.util.Collection; import java.util.List; import java.util.zip.GZIPInputStream; import com.datos.vfs.Selectors; import com.datos.vfs.VfsLog; import org.apache.commons.compress.archivers.tar.TarArchiveEntry; import org.apache.commons.compress.archivers.tar.TarArchiveInputStream; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import com.datos.vfs.Capability; import com.datos.vfs.FileObject; import com.datos.vfs.FileSystemException; import com.datos.vfs.FileSystemOptions; import com.datos.vfs.provider.AbstractFileName; import com.datos.vfs.provider.AbstractFileSystem; import com.datos.vfs.provider.UriParser; import com.datos.vfs.provider.bzip2.Bzip2FileObject; /** * A read-only file system for Tar files. */ public class TarFileSystem extends AbstractFileSystem { private static final int DEFAULT_INDEX_SIZE = 100; private static final Log LOG = LogFactory.getLog(TarFileSystem.class); private final File file; private TarArchiveInputStream tarFile; protected TarFileSystem(final AbstractFileName rootName, final FileObject parentLayer, final FileSystemOptions fileSystemOptions) throws FileSystemException { super(rootName, parentLayer, fileSystemOptions); // Make a local copy of the file file = parentLayer.getFileSystem().replicateFile(parentLayer, Selectors.SELECT_SELF); // Open the Tar file if (!file.exists()) { // Don't need to do anything tarFile = null; return; } // tarFile = createTarFile(this.file); } @Override public void init() throws FileSystemException { super.init(); // Build the index try { final List<TarFileObject> strongRef = new ArrayList<>(DEFAULT_INDEX_SIZE); TarArchiveEntry entry; while ((entry = getTarFile().getNextTarEntry()) != null) { final AbstractFileName name = (AbstractFileName) getFileSystemManager().resolveName(getRootName(), UriParser.encode(entry.getName())); // Create the file TarFileObject fileObj; if (entry.isDirectory() && getFileFromCache(name) != null) { fileObj = (TarFileObject) getFileFromCache(name); fileObj.setTarEntry(entry); continue; } fileObj = createTarFileObject(name, entry); putFileToCache(fileObj); strongRef.add(fileObj); fileObj.holdObject(strongRef); // Make sure all ancestors exist // TODO - create these on demand TarFileObject parent = null; for (AbstractFileName parentName = (AbstractFileName) name .getParent(); parentName != null; fileObj = parent, parentName = (AbstractFileName) parentName .getParent()) { // Locate the parent parent = (TarFileObject) getFileFromCache(parentName); if (parent == null) { parent = createTarFileObject(parentName, null); putFileToCache(parent); strongRef.add(parent); parent.holdObject(strongRef); } // Attach child to parent parent.attachChild(fileObj.getName()); } } } catch (final IOException e) { throw new FileSystemException(e); } finally { closeCommunicationLink(); } } public InputStream getInputStream(final TarArchiveEntry entry) throws FileSystemException { resetTarFile(); try { while (!tarFile.getNextEntry().equals(entry)) { } return tarFile; } catch (final IOException e) { throw new FileSystemException(e); } } protected void resetTarFile() throws FileSystemException { // Reading specific entries requires skipping through the tar file from the beginning // Not especially elegant, but we don't have the ability to seek to specific positions // with an input stream. if (this.file.exists()) { recreateTarFile(); } } private void recreateTarFile() throws FileSystemException { if (this.tarFile != null) { try { this.tarFile.close(); } catch (final IOException e) { throw new FileSystemException("vfs.provider.tar/close-tar-file.error", file, e); } tarFile = null; } final TarArchiveInputStream tarFile = createTarFile(this.file); this.tarFile = tarFile; } protected TarArchiveInputStream getTarFile() throws FileSystemException { if (tarFile == null && this.file.exists()) { recreateTarFile(); } return tarFile; } protected TarFileObject createTarFileObject(final AbstractFileName name, final TarArchiveEntry entry) throws FileSystemException { return new TarFileObject(name, entry, this, true); } protected TarArchiveInputStream createTarFile(final File file) throws FileSystemException { try { if ("tgz".equalsIgnoreCase(getRootName().getScheme())) { return new TarArchiveInputStream(new GZIPInputStream(new FileInputStream(file))); } else if ("tbz2".equalsIgnoreCase(getRootName().getScheme())) { return new TarArchiveInputStream( Bzip2FileObject.wrapInputStream(file.getAbsolutePath(), new FileInputStream(file))); } return new TarArchiveInputStream(new FileInputStream(file)); } catch (final IOException ioe) { throw new FileSystemException("vfs.provider.tar/open-tar-file.error", file, ioe); } } @Override protected void doCloseCommunicationLink() { // Release the tar file try { if (tarFile != null) { tarFile.close(); tarFile = null; } } catch (final IOException e) { // getLogger().warn("vfs.provider.tar/close-tar-file.error :" + file, e); VfsLog.warn(getLogger(), LOG, "vfs.provider.tar/close-tar-file.error :" + file, e); } } /** * Returns the capabilities of this file system. */ @Override protected void addCapabilities(final Collection<Capability> caps) { caps.addAll(TarFileProvider.capabilities); } /** * Creates a file object. */ @Override protected FileObject createFile(final AbstractFileName name) throws FileSystemException { // This is only called for files which do not exist in the Tar file return new TarFileObject(name, null, this, false); } /** * will be called after all file-objects closed their streams. protected void notifyAllStreamsClosed() { closeCommunicationLink(); } */ }