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.commons.vfs2.provider; import java.io.File; import java.lang.reflect.InvocationTargetException; import java.util.ArrayList; import java.util.Collection; import java.util.HashMap; import java.util.HashSet; import java.util.Map; import java.util.concurrent.atomic.AtomicInteger; import java.util.concurrent.atomic.AtomicLong; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.commons.vfs2.CacheStrategy; import org.apache.commons.vfs2.Capability; import org.apache.commons.vfs2.FileListener; import org.apache.commons.vfs2.FileName; import org.apache.commons.vfs2.FileObject; import org.apache.commons.vfs2.FileSelector; import org.apache.commons.vfs2.FileSystem; import org.apache.commons.vfs2.FileSystemConfigBuilder; import org.apache.commons.vfs2.FileSystemException; import org.apache.commons.vfs2.FileSystemManager; import org.apache.commons.vfs2.FileSystemOptions; import org.apache.commons.vfs2.FilesCache; import org.apache.commons.vfs2.VfsLog; import org.apache.commons.vfs2.cache.OnCallRefreshFileObject; import org.apache.commons.vfs2.events.AbstractFileChangeEvent; import org.apache.commons.vfs2.events.ChangedEvent; import org.apache.commons.vfs2.events.CreateEvent; import org.apache.commons.vfs2.events.DeleteEvent; import org.apache.commons.vfs2.impl.DefaultFileSystemConfigBuilder; import org.apache.commons.vfs2.util.Messages; /** * A partial {@link org.apache.commons.vfs2.FileSystem} implementation. */ public abstract class AbstractFileSystem extends AbstractVfsComponent implements FileSystem { private static final Log LOG = LogFactory.getLog(AbstractFileSystem.class); /** * The "root" of the file system. This is always "/" so it isn't always the "real" * root. */ private final FileName rootName; /** * The root URI of the file system. The base path specified as a file system option * when the file system was created. */ private final String rootURI; private final Collection<Capability> caps = new HashSet<Capability>(); private FileObject parentLayer; /** * Map from FileName to an ArrayList of listeners for that file. */ private final Map<FileName, ArrayList<FileListener>> listenerMap = new HashMap<FileName, ArrayList<FileListener>>(); /** * FileSystemOptions used for configuration */ private final FileSystemOptions fileSystemOptions; /** * How many fileObjects are handed out */ private final AtomicLong useCount = new AtomicLong(0); private FileSystemKey cacheKey; /** * open streams counter for this filesystem */ private final AtomicInteger openStreams = new AtomicInteger(0); protected AbstractFileSystem(final FileName rootName, final FileObject parentLayer, final FileSystemOptions fileSystemOptions) { this.parentLayer = parentLayer; this.rootName = rootName; this.fileSystemOptions = fileSystemOptions; final FileSystemConfigBuilder builder = DefaultFileSystemConfigBuilder.getInstance(); String uri = builder.getRootURI(fileSystemOptions); if (uri == null) { uri = rootName.getURI(); } this.rootURI = uri; } /** * Initializes this component. * @throws FileSystemException if an error occurs. */ @Override public void init() throws FileSystemException { addCapabilities(caps); } /** * Closes this component. */ @Override public void close() { closeCommunicationLink(); parentLayer = null; } /** * Close the underlying link used to access the files. */ public void closeCommunicationLink() { synchronized (this) { doCloseCommunicationLink(); } } /** * Close the underlying link used to access the files */ protected void doCloseCommunicationLink() { } /** * Creates a file object. * <p> * This method is called only if the requested file is not cached. * * @param name name referencing the new file. * @return new created FileObject. * @throws Exception might throw an Exception, which is then wrapped in FileSystemException. */ protected abstract FileObject createFile(final AbstractFileName name) throws Exception; /** * Adds the capabilities of this file system. * * @param caps collections of Capabilities, can be immutable. */ protected abstract void addCapabilities(Collection<Capability> caps); /** * Returns the name of the root of this file system. * @return the root FileName. */ @Override public FileName getRootName() { return rootName; } /** * Returns the root URI specified for this file System. * @return The root URI used in this file system. * @since 2.0 */ @Override public String getRootURI() { return rootURI; } /** * Adds a file object to the cache. * @param file the file to add. */ protected void putFileToCache(final FileObject file) { getCache().putFile(file); } private FilesCache getCache() { FilesCache files; files = getContext().getFileSystemManager().getFilesCache(); if (files == null) { throw new RuntimeException(Messages.getString("vfs.provider/files-cache-missing.error")); } return files; } /** * Returns a cached file. * @param name name to search for. * @return file object or null if not found. */ protected FileObject getFileFromCache(final FileName name) { return getCache().getFile(this, name); } /** * Remove a cached file. * @param name The file name to remove. */ protected void removeFileFromCache(final FileName name) { getCache().removeFile(this, name); } /** * Determines if this file system has a particular capability. * @param capability the Capability to check for. * @return true if the FileSystem has the Capability, false otherwise. */ @Override public boolean hasCapability(final Capability capability) { return caps.contains(capability); } /** * Retrieves the attribute with the specified name. The default * implementation simply throws an exception. * @param attrName The name of the attribute. * @return the Object associated with the attribute or null if no object is. * @throws FileSystemException if an error occurs. */ @Override public Object getAttribute(final String attrName) throws FileSystemException { throw new FileSystemException("vfs.provider/get-attribute-not-supported.error"); } /** * Sets the attribute with the specified name. The default * implementation simply throws an exception. * @param attrName the attribute name. * @param value The object to associate with the attribute. * @throws FileSystemException if an error occurs. */ @Override public void setAttribute(final String attrName, final Object value) throws FileSystemException { throw new FileSystemException("vfs.provider/set-attribute-not-supported.error"); } /** * Returns the parent layer if this is a layered file system. * @return The FileObject for the parent layer. * @throws FileSystemException if an error occurs. */ @Override public FileObject getParentLayer() throws FileSystemException { return parentLayer; } /** * Returns the root file of this file system. * @return The root FileObject of the FileSystem * @throws FileSystemException if an error occurs. */ @Override public FileObject getRoot() throws FileSystemException { return resolveFile(rootName); } /** * Finds a file in this file system. * @param nameStr The name of the file to resolve. * @return The located FileObject or null if none could be located. * @throws FileSystemException if an error occurs. */ @Override public FileObject resolveFile(final String nameStr) throws FileSystemException { // Resolve the name, and create the file final FileName name = getFileSystemManager().resolveName(rootName, nameStr); return resolveFile(name); } /** * Finds a file in this file system. * @param name The name of the file to locate. * @return The located FileObject or null if none could be located. * @throws FileSystemException if an error occurs. */ @Override public FileObject resolveFile(final FileName name) throws FileSystemException { return resolveFile(name, true); } private synchronized FileObject resolveFile(final FileName name, final boolean useCache) throws FileSystemException { if (!rootName.getRootURI().equals(name.getRootURI())) { throw new FileSystemException("vfs.provider/mismatched-fs-for-name.error", name, rootName, name.getRootURI()); } // imario@apache.org ==> use getFileFromCache FileObject file; if (useCache) { file = getFileFromCache(name); } else { file = null; } if (file == null) { try { file = createFile((AbstractFileName) name); } catch (final Exception e) { throw new FileSystemException("vfs.provider/resolve-file.error", name, e); } file = decorateFileObject(file); // imario@apache.org ==> use putFileToCache if (useCache) { putFileToCache(file); } } /** * resync the file information if requested */ if (getFileSystemManager().getCacheStrategy().equals(CacheStrategy.ON_RESOLVE)) { file.refresh(); } return file; } protected FileObject decorateFileObject(FileObject file) throws FileSystemException { if (getFileSystemManager().getCacheStrategy().equals(CacheStrategy.ON_CALL)) { file = new OnCallRefreshFileObject(file); } if (getFileSystemManager().getFileObjectDecoratorConst() != null) { try { file = (FileObject) getFileSystemManager().getFileObjectDecoratorConst() .newInstance(new Object[] { file }); } catch (final InstantiationException e) { throw new FileSystemException("vfs.impl/invalid-decorator.error", getFileSystemManager().getFileObjectDecorator().getName(), e); } catch (final IllegalAccessException e) { throw new FileSystemException("vfs.impl/invalid-decorator.error", getFileSystemManager().getFileObjectDecorator().getName(), e); } catch (final InvocationTargetException e) { throw new FileSystemException("vfs.impl/invalid-decorator.error", getFileSystemManager().getFileObjectDecorator().getName(), e); } } return file; } /** * Creates a temporary local copy of a file and its descendants. * @param file The FileObject to replicate. * @param selector The FileSelector. * @return The replicated File. * @throws FileSystemException if an error occurs. */ @Override public File replicateFile(final FileObject file, final FileSelector selector) throws FileSystemException { if (!file.exists()) { throw new FileSystemException("vfs.provider/replicate-missing-file.error", file.getName()); } try { return doReplicateFile(file, selector); } catch (final Exception e) { throw new FileSystemException("vfs.provider/replicate-file.error", file.getName(), e); } } /** * Return the FileSystemOptions used to instantiate this filesystem. * @return the FileSystemOptions. */ @Override public FileSystemOptions getFileSystemOptions() { return fileSystemOptions; } /** * Return the FileSystemManager used to instantiate this filesystem. * @return the FileSystemManager. */ @Override public FileSystemManager getFileSystemManager() { return getContext().getFileSystemManager(); } /** * Returns the accuracy of the last modification time. * * @return ms 0 perfectly accurate, {@literal >0} might be off by this value e.g. sftp 1000ms */ @Override public double getLastModTimeAccuracy() { return 0; } /** * Creates a temporary local copy of a file and its descendants. * * @param file the start of the tree. * @param selector selection what to do with childs. * @return replicated root file. * @throws Exception any Exception is wrapped as FileSystemException. */ protected File doReplicateFile(final FileObject file, final FileSelector selector) throws Exception { return getContext().getReplicator().replicateFile(file, selector); } /** * Adds a junction to this file system. * @param junctionPoint The junction point. * @param targetFile The target to add. * @throws FileSystemException if an error occurs. */ @Override public void addJunction(final String junctionPoint, final FileObject targetFile) throws FileSystemException { throw new FileSystemException("vfs.provider/junctions-not-supported.error", rootName); } /** * Removes a junction from this file system. * @param junctionPoint The junction point. * @throws FileSystemException if an error occurs */ @Override public void removeJunction(final String junctionPoint) throws FileSystemException { throw new FileSystemException("vfs.provider/junctions-not-supported.error", rootName); } /** * Adds a listener on a file in this file system. * @param file The FileObject to be monitored. * @param listener The FileListener */ @Override public void addListener(final FileObject file, final FileListener listener) { synchronized (listenerMap) { ArrayList<FileListener> listeners = listenerMap.get(file.getName()); if (listeners == null) { listeners = new ArrayList<FileListener>(); listenerMap.put(file.getName(), listeners); } listeners.add(listener); } } /** * Removes a listener from a file in this file system. * @param file The FileObject to be monitored. * @param listener The FileListener */ @Override public void removeListener(final FileObject file, final FileListener listener) { synchronized (listenerMap) { final ArrayList<?> listeners = listenerMap.get(file.getName()); if (listeners != null) { listeners.remove(listener); if (listeners.isEmpty()) { listenerMap.remove(file.getName()); } } } } /** * Fires a file create event. * @param file The FileObject that was created. */ public void fireFileCreated(final FileObject file) { fireEvent(new CreateEvent(file)); } /** * Fires a file delete event. * @param file The FileObject that was deleted. */ public void fireFileDeleted(final FileObject file) { fireEvent(new DeleteEvent(file)); } /** * Fires a file changed event. * <p> * This will only happen if you monitor the file using {@link org.apache.commons.vfs2.FileMonitor}. * * @param file The FileObject that changed. */ public void fireFileChanged(final FileObject file) { fireEvent(new ChangedEvent(file)); } /** * Returns true if no file is using this filesystem. * * @return true if no file is using this FileSystem. */ public boolean isReleaseable() { return useCount.get() < 1; } void freeResources() { } /** * Fires an event. */ private void fireEvent(final AbstractFileChangeEvent event) { FileListener[] fileListeners = null; final FileObject file = event.getFile(); synchronized (listenerMap) { final ArrayList<?> listeners = listenerMap.get(file.getName()); if (listeners != null) { fileListeners = listeners.toArray(new FileListener[listeners.size()]); } } if (fileListeners != null) { for (final FileListener fileListener : fileListeners) { try { event.notify(fileListener); } catch (final Exception e) { final String message = Messages.getString("vfs.provider/notify-listener.warn", file); // getLogger().warn(message, e); VfsLog.warn(getLogger(), LOG, message, e); } } } } void fileObjectHanded(final FileObject fileObject) { useCount.incrementAndGet(); } void fileObjectDestroyed(final FileObject fileObject) { useCount.decrementAndGet(); } void setCacheKey(final FileSystemKey cacheKey) { this.cacheKey = cacheKey; } FileSystemKey getCacheKey() { return this.cacheKey; } void streamOpened() { openStreams.incrementAndGet(); } void streamClosed() { int count; do { count = openStreams.get(); if (count < 1) { return; } } while (openStreams.compareAndSet(count, count - 1)); if (count == 1) { notifyAllStreamsClosed(); } } /** * will be called after all file-objects closed their streams. */ protected void notifyAllStreamsClosed() { } /** * check if this filesystem has open streams. * @return true if the FileSystem has open streams. */ public boolean isOpen() { return openStreams.get() > 0; } }