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.InputStream; import java.io.OutputStream; import java.security.cert.Certificate; import java.util.HashSet; import java.util.Map; import java.util.Set; import org.apache.commons.vfs2.FileChangeEvent; import org.apache.commons.vfs2.FileContentInfo; import org.apache.commons.vfs2.FileListener; import org.apache.commons.vfs2.FileName; import org.apache.commons.vfs2.FileNotFolderException; import org.apache.commons.vfs2.FileObject; import org.apache.commons.vfs2.FileSystemException; import org.apache.commons.vfs2.FileType; import org.apache.commons.vfs2.RandomAccessContent; import org.apache.commons.vfs2.util.RandomAccessMode; import org.apache.commons.vfs2.util.WeakRefFileListener; /** * A file backed by another file. * <p> * TODO - Extract subclass that overlays the children. * * @param <AFS> A subclass of AbstractFileSystem. */ public class DelegateFileObject<AFS extends AbstractFileSystem> extends AbstractFileObject<AFS> implements FileListener { private FileObject file; private final Set<String> children = new HashSet<String>(); private boolean ignoreEvent; public DelegateFileObject(final AbstractFileName name, final AFS fileSystem, final FileObject file) throws FileSystemException { super(name, fileSystem); this.file = file; if (file != null) { WeakRefFileListener.installListener(file, this); } } /** * Get access to the delegated file. * @return The FileObject. * @since 2.0 */ public FileObject getDelegateFile() { return file; } /** * Adds a child to this file. * @param baseName The base FileName. * @param type The FileType. * @throws Exception if an error occurs. */ public void attachChild(final FileName baseName, final FileType type) throws Exception { final FileType oldType = doGetType(); if (children.add(baseName.getBaseName())) { childrenChanged(baseName, type); } maybeTypeChanged(oldType); } /** * Attaches or detaches the target file. * @param file The FileObject. * @throws Exception if an error occurs. */ public void setFile(final FileObject file) throws Exception { final FileType oldType = doGetType(); if (file != null) { WeakRefFileListener.installListener(file, this); } this.file = file; maybeTypeChanged(oldType); } /** * Checks whether the file's type has changed, and fires the appropriate * events. * @param oldType The old FileType. * @throws Exception if an error occurs. */ private void maybeTypeChanged(final FileType oldType) throws Exception { final FileType newType = doGetType(); if (oldType == FileType.IMAGINARY && newType != FileType.IMAGINARY) { handleCreate(newType); } else if (oldType != FileType.IMAGINARY && newType == FileType.IMAGINARY) { handleDelete(); } } /** * Determines the type of the file, returns null if the file does not * exist. */ @Override protected FileType doGetType() throws FileSystemException { if (file != null) { return file.getType(); } else if (children.size() > 0) { return FileType.FOLDER; } else { return FileType.IMAGINARY; } } /** * Determines if this file can be read. */ @Override protected boolean doIsReadable() throws FileSystemException { if (file != null) { return file.isReadable(); } else { return true; } } /** * Determines if this file can be written to. */ @Override protected boolean doIsWriteable() throws FileSystemException { if (file != null) { return file.isWriteable(); } else { return false; } } /** * Determines if this file is executable. */ @Override protected boolean doIsExecutable() throws FileSystemException { if (file != null) { return file.isExecutable(); } else { return false; } } /** * Determines if this file is hidden. */ @Override protected boolean doIsHidden() throws FileSystemException { if (file != null) { return file.isHidden(); } else { return false; } } /** * Lists the children of the file. */ @Override protected String[] doListChildren() throws Exception { if (file != null) { final FileObject[] children; try { children = file.getChildren(); } // VFS-210 catch (final FileNotFolderException e) { throw new FileNotFolderException(getName(), e); } final String[] childNames = new String[children.length]; for (int i = 0; i < children.length; i++) { childNames[i] = children[i].getName().getBaseName(); } return childNames; } else { return children.toArray(new String[children.size()]); } } /** * Creates this file as a folder. */ @Override protected void doCreateFolder() throws Exception { ignoreEvent = true; try { file.createFolder(); } finally { ignoreEvent = false; } } /** * Deletes the file. */ @Override protected void doDelete() throws Exception { ignoreEvent = true; try { file.delete(); } finally { ignoreEvent = false; } } /** * Returns the size of the file content (in bytes). Is only called if * {@link #doGetType} returns {@link FileType#FILE}. */ @Override protected long doGetContentSize() throws Exception { return file.getContent().getSize(); } /** * Returns the attributes of this file. */ @Override protected Map<String, Object> doGetAttributes() throws Exception { return file.getContent().getAttributes(); } /** * Sets an attribute of this file. */ @Override protected void doSetAttribute(final String atttrName, final Object value) throws Exception { file.getContent().setAttribute(atttrName, value); } /** * Returns the certificates of this file. */ @Override protected Certificate[] doGetCertificates() throws Exception { return file.getContent().getCertificates(); } /** * Returns the last-modified time of this file. */ @Override protected long doGetLastModifiedTime() throws Exception { return file.getContent().getLastModifiedTime(); } /** * Sets the last-modified time of this file. * @since 2.0 */ @Override protected boolean doSetLastModifiedTime(final long modtime) throws Exception { file.getContent().setLastModifiedTime(modtime); return true; } /** * Creates an input stream to read the file content from. */ @Override protected InputStream doGetInputStream() throws Exception { return file.getContent().getInputStream(); } /** * Creates an output stream to write the file content to. */ @Override protected OutputStream doGetOutputStream(final boolean bAppend) throws Exception { return file.getContent().getOutputStream(bAppend); } /** * Called when a file is created. * @param event The FileChangeEvent. * @throws Exception if an error occurs. */ @Override public void fileCreated(final FileChangeEvent event) throws Exception { if (event.getFile() != file) { return; } if (!ignoreEvent) { handleCreate(file.getType()); } } /** * Called when a file is deleted. * @param event The FileChangeEvent. * @throws Exception if an error occurs. */ @Override public void fileDeleted(final FileChangeEvent event) throws Exception { if (event.getFile() != file) { return; } if (!ignoreEvent) { handleDelete(); } } /** * Called when a file is changed. * <p> * This will only happen if you monitor the file using {@link org.apache.commons.vfs2.FileMonitor}. * * @param event The FileChangeEvent. * @throws Exception if an error occurs. */ @Override public void fileChanged(final FileChangeEvent event) throws Exception { if (event.getFile() != file) { return; } if (!ignoreEvent) { handleChanged(); } } /** * Close the delegated file. * @throws FileSystemException if an error occurs. */ @Override public void close() throws FileSystemException { super.close(); if (file != null) { file.close(); } } /** * Refresh file information. * @throws FileSystemException if an error occurs. * @since 2.0 */ @Override public void refresh() throws FileSystemException { super.refresh(); if (file != null) { file.refresh(); } } /** * Return file content info. * @return the file content info of the delegee. * @throws Exception Any thrown Exception is wrapped in FileSystemException. * @since 2.0 */ protected FileContentInfo doGetContentInfo() throws Exception { return file.getContent().getContentInfo(); } /** * Renames the file. * * @param newFile the new location/name. * @throws Exception Any thrown Exception is wrapped in FileSystemException. * @since 2.0 */ @Override protected void doRename(final FileObject newFile) throws Exception { file.moveTo(((DelegateFileObject) newFile).file); } /** * Removes an attribute of this file. * @since 2.0 */ @Override protected void doRemoveAttribute(final String atttrName) throws Exception { file.getContent().removeAttribute(atttrName); } /** * Creates access to the file for random i/o. * @since 2.0 */ @Override protected RandomAccessContent doGetRandomAccessContent(final RandomAccessMode mode) throws Exception { return file.getContent().getRandomAccessContent(mode); } }