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.vfs; import java.net.URL; import java.util.List; import org.apache.commons.vfs.operations.FileOperations; /** * Represents a file, and is used to access the content and * structure of the file. * <p/> * <p>Files are arranged in a hierarchy. Each hierachy forms a * <i>file system</i>. A file system represents things like a local OS * file system, a windows share, an HTTP server, or the contents of a Zip file. * <p/> * <p>There are two types of files: <i>Folders</i>, which contain other files, * and <i>normal files</i>, which contain data, or <i>content</i>. A folder may * not have any content, and a normal file cannot contain other files. * <p/> * <h4>File Naming</h4> * <p/> * <p>TODO - write this. * <p/> * <h4>Reading and Writing a File</h4> * <p/> * <p>Reading and writing a file, and all other operations on the file's * <i>content</i>, is done using the {@link FileContent} object returned * by {@link #getContent}. * <p/> * <h4>Creating and Deleting a File</h4> * <p/> * <p>A file is created using either {@link #createFolder}, {@link #createFile}, * or by writing to the file using one of the {@link FileContent} methods. * <p/> * <p>A file is deleted using {@link #delete}. Recursive deletion can be * done using {@link #delete(FileSelector)}. * <p/> * <h4>Finding Files</h4> * <p/> * <p>Other files in the <i>same</i> file system as this file can be found * using: * <ul> * <li>{@link #resolveFile} to find another file relative to this file. * <li>{@link #getChildren} and {@link #getChild} to find the children of this file. * <li>{@link #getParent} to find the folder containing this file. * <li>{@link #getFileSystem} to find another file in the same file system. * </ul> * <p/> * <p>To find files in another file system, use a {@link FileSystemManager}. * * @author <a href="mailto:adammurdoch@apache.org">Adam Murdoch</a> * @version $Revision$ $Date$ * @see FileSystemManager * @see FileContent * @see FileName */ public interface FileObject { /** * Returns the name of this file. */ public FileName getName(); /** * Returns a URL representing this file. */ public URL getURL() throws FileSystemException; /** * Determines if this file exists. * * @return <code>true</code> if this file exists, <code>false</code> if not. * @throws FileSystemException On error determining if this file exists. */ public boolean exists() throws FileSystemException; /** * Determines if this file is hidden. * * @return <code>true</code> if this file is hidden, <code>false</code> if not. * @throws FileSystemException On error determining if this file exists. */ public boolean isHidden() throws FileSystemException; /** * Determines if this file can be read. * * @return <code>true</code> if this file is readable, <code>false</code> if not. * @throws FileSystemException On error determining if this file exists. */ public boolean isReadable() throws FileSystemException; /** * Determines if this file can be written to. * * @return <code>true</code> if this file is writeable, <code>false</code> if not. * @throws FileSystemException On error determining if this file exists. */ public boolean isWriteable() throws FileSystemException; /** * Returns this file's type. * * @return One of the {@link FileType} constants. Never returns null. * @throws FileSystemException On error determining the file's type. */ public FileType getType() throws FileSystemException; /** * Returns the folder that contains this file. * * @return The folder that contains this file. Returns null if this file is * the root of a file system. * @throws FileSystemException On error finding the file's parent. */ public FileObject getParent() throws FileSystemException; /** * Returns the file system that contains this file. * * @return The file system. */ public FileSystem getFileSystem(); /** * Lists the children of this file. * * @return An array containing the children of this file. The array is * unordered. If the file does not have any children, a zero-length * array is returned. This method never returns null. * @throws FileSystemException If this file does not exist, or is not a folder, or on error * listing this file's children. */ public FileObject[] getChildren() throws FileSystemException; /** * Returns a child of this file. Note that this method returns <code>null</code> * when the child does not exist. This differs from * {@link #resolveFile( String, NameScope)} which never returns null. * * @param name The name of the child. * @return The child, or null if there is no such child. * @throws FileSystemException If this file does not exist, or is not a folder, or on error * determining this file's children. */ public FileObject getChild(String name) throws FileSystemException; /** * Finds a file, relative to this file. Refer to {@link NameScope} * for a description of how names are resolved in the different scopes. * * @param name The name to resolve. * @return The file. * @throws FileSystemException On error parsing the path, or on error finding the file. */ public FileObject resolveFile(String name, NameScope scope) throws FileSystemException; /** * Finds a file, relative to this file. Equivalent to calling * <code>resolveFile( path, NameScope.FILE_SYSTEM )</code>. * * @param path The path of the file to locate. Can either be a relative * path or an absolute path. * @return The file. * @throws FileSystemException On error parsing the path, or on error finding the file. */ public FileObject resolveFile(String path) throws FileSystemException; /** * Finds the set of matching descendents of this file, in depthwise order. * * @param selector The selector to use to select matching files. * @return The matching files. The files are returned in depthwise order * (that is, a child appears in the list before its parent). */ public FileObject[] findFiles(FileSelector selector) throws FileSystemException; /** * Finds the set of matching descendents of this file. * * @param selector the selector used to determine if the file should be selected * @param depthwise controls the ordering in the list. e.g. deepest first * @param selected container for selected files. list needs not to be empty. * @throws FileSystemException */ public void findFiles(FileSelector selector, boolean depthwise, List selected) throws FileSystemException; /** * Deletes this file. Does nothing if this file does not exist of if it is a * folder that has children. Does not delete any descendents of this file, * use {@link #delete(FileSelector)} for that. * * @return true if this object has been deleted * @throws FileSystemException If this file is a non-empty folder, or if this file is read-only, * or on error deleteing this file. */ public boolean delete() throws FileSystemException; /** * Deletes all descendents of this file that match a selector. Does * nothing if this file does not exist. * <p/> * <p>This method is not transactional. If it fails and throws an * exception, this file will potentially only be partially deleted. * * @param selector The selector to use to select which files to delete. * @return the number of deleted objects * @throws FileSystemException If this file or one of its descendents is read-only, or on error * deleting this file or one of its descendents. */ public int delete(FileSelector selector) throws FileSystemException; /** * Creates this folder, if it does not exist. Also creates any ancestor * folders which do not exist. This method does nothing if the folder * already exists. * * @throws FileSystemException If the folder already exists with the wrong type, or the parent * folder is read-only, or on error creating this folder or one of * its ancestors. */ public void createFolder() throws FileSystemException; /** * Creates this file, if it does not exist. Also creates any ancestor * folders which do not exist. This method does nothing if the file * already exists and is a file. * * @throws FileSystemException If the file already exists with the wrong type, or the parent * folder is read-only, or on error creating this file or one of * its ancestors. */ public void createFile() throws FileSystemException; /** * Copies another file, and all its descendents, to this file. * <p/> * If this file does not exist, it is created. Its parent folder is also * created, if necessary. If this file does exist, it is deleted first. * <p/> * <p>This method is not transactional. If it fails and throws an * exception, this file will potentially only be partially copied. * * @param srcFile The source file to copy. * @param selector The selector to use to select which files to copy. * @throws FileSystemException If this file is read-only, or if the source file does not exist, * or on error copying the file. */ public void copyFrom(FileObject srcFile, FileSelector selector) throws FileSystemException; /** * Move this file. * <p>If the destFile exists, it is deleted first</b> * * @param destFile the New filename. * @throws FileSystemException If this file is read-only, or if the source file does not exist, * or on error copying the file. */ public void moveTo(FileObject destFile) throws FileSystemException; /** * Queries the file if it is possible to rename it to newfile. * * @param newfile the new file(-name) * @return true it this is the case */ public boolean canRenameTo(FileObject newfile); /** * Returns this file's content. The {@link FileContent} returned by this * method can be used to read and write the content of the file. * <p/> * <p>This method can be called if the file does not exist, and * the returned {@link FileContent} can be used to create the file * by writing its content. * * @return This file's content. * @throws FileSystemException On error getting this file's content. */ public FileContent getContent() throws FileSystemException; /** * Closes this file, and its content. This method is a hint to the * implementation that it can release any resources associated with * the file. * <p/> * <p>The file object can continue to be used after this method is called. * * @throws FileSystemException On error closing the file. * @see FileContent#close */ public void close() throws FileSystemException; /** * This will prepare the fileObject to get resynchronized with the underlaying filesystem if required */ public void refresh() throws FileSystemException; /** * check if the fileObject is attaced */ public boolean isAttached(); /** * check if someone reads/write to this file */ public boolean isContentOpen(); // --- OPERATIONS -- /** * @return FileOperations interface that provides access to the operations API. * @throws FileSystemException */ FileOperations getFileOperations() throws FileSystemException; }