001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.vfs2;
018
019import java.io.File;
020
021/**
022 * A file system, made up of a hierarchy of files.
023 */
024public interface FileSystem {
025    /**
026     * Returns the root file of this file system.
027     *
028     * @return The root FileObject.
029     * @throws FileSystemException if an error occurs.
030     */
031    FileObject getRoot() throws FileSystemException;
032
033    /**
034     * Returns the name of the root file of this file system. The root name always contains a path String of "/".
035     *
036     * @return the root FileName.
037     */
038    FileName getRootName();
039
040    /**
041     * The root URI passed as a file system option or obtained from the rootName.
042     *
043     * @return The root URI.
044     */
045    String getRootURI();
046
047    /**
048     * Determines if this file system has a particular capability.
049     * <p>
050     * TODO - Move this to another interface, so that set of capabilities can be queried.
051     *
052     * @param capability The capability to check for.
053     * @return true if this filesystem has the requested capability. Note that not all files in the file system may have
054     *         the capability.
055     */
056    boolean hasCapability(Capability capability);
057
058    /**
059     * Returns the parent layer if this is a layered file system.
060     *
061     * @return The parent layer, or null if this is not a layered file system.
062     * @throws FileSystemException if an error occurs.
063     */
064    FileObject getParentLayer() throws FileSystemException;
065
066    /**
067     * Gets the value of an attribute of the file system.
068     * <p>
069     * TODO - change to {@code Map getAttributes()} instead?<br>
070     * TODO - define the standard attribute names, and define which attrs are guaranteed to be present.
071     *
072     * @param attrName The name of the attribute.
073     * @return The value of the attribute.
074     * @throws org.apache.commons.vfs2.FileSystemException If the file does not exist, or is being written, or if the
075     *             attribute is unknown.
076     * @see org.apache.commons.vfs2.FileContent#getAttribute
077     */
078    Object getAttribute(String attrName) throws FileSystemException;
079
080    /**
081     * Sets the value of an attribute of the file's content. Creates the file if it does not exist.
082     *
083     * @param attrName The name of the attribute.
084     * @param value The value of the attribute.
085     * @throws FileSystemException If the file is read-only, or is being read, or if the attribute is not supported, or
086     *             on error setting the attribute.
087     * @see FileContent#setAttribute
088     */
089    void setAttribute(String attrName, Object value) throws FileSystemException;
090
091    /**
092     * Finds a file in this file system.
093     *
094     * @param name The name of the file.
095     * @return The file. Never returns null.
096     * @throws FileSystemException if an error occurs.
097     */
098    FileObject resolveFile(FileName name) throws FileSystemException;
099
100    /**
101     * Finds a file in this file system.
102     *
103     * @param name The name of the file. This must be an absolute path.
104     * @return The file. Never returns null.
105     * @throws FileSystemException if an error occurs.
106     */
107    FileObject resolveFile(String name) throws FileSystemException;
108
109    /**
110     * Adds a listener on a file in this file system.
111     *
112     * @param file The file to attach the listener to.
113     * @param listener The listener to add.
114     */
115    void addListener(FileObject file, FileListener listener);
116
117    /**
118     * Removes a listener from a file in this file system.
119     *
120     * @param file The file to remove the listener from.
121     * @param listener The listener to remove.
122     */
123    void removeListener(FileObject file, FileListener listener);
124
125    /**
126     * Adds a junction to this file system. A junction is a link that attaches the supplied file to a point in this file
127     * system, making it look like part of the file system.
128     *
129     * @param junctionPoint The point in this file system to add the junction.
130     * @param targetFile The file to link to.
131     * @throws FileSystemException If this file system does not support junctions, or the junction point or target file
132     *             is invalid (the file system may not support nested junctions, for example).
133     */
134    void addJunction(String junctionPoint, FileObject targetFile) throws FileSystemException;
135
136    /**
137     * Removes a junction from this file system.
138     *
139     * @param junctionPoint The junction to remove.
140     * @throws FileSystemException On error removing the junction.
141     */
142    void removeJunction(String junctionPoint) throws FileSystemException;
143
144    /**
145     * Creates a temporary local copy of a file and its descendants. If this file is already a local file, a copy is not
146     * made.
147     * <p>
148     * Note that the local copy may include additonal files, that were not selected by the given selector.
149     * <p>
150     * TODO - Add options to indicate whether the caller is happy to deal with extra files being present locally (eg if
151     * the file has been replicated previously), or whether the caller expects only the selected files to be present.
152     *
153     * @param file The file to replicate.
154     * @param selector The selector to use to select the files to replicate.
155     * @return The local copy of this file.
156     * @throws FileSystemException If this file does not exist, or on error replicating the file.
157     */
158    File replicateFile(FileObject file, FileSelector selector) throws FileSystemException;
159
160    /**
161     * Returns the FileSystemOptions used to instantiate this filesystem.
162     *
163     * @return The FileSystemOptions.
164     */
165    FileSystemOptions getFileSystemOptions();
166
167    /**
168     * Returns a reference to the FileSytemManager.
169     *
170     * @return The FileSystemManager.
171     */
172    FileSystemManager getFileSystemManager();
173
174    /**
175     * Returns the accuracy of the last modification time.
176     * <p>
177     * The local file provider is not very smart in figuring this out, for remote access to file systems the providers
178     * typically don't know the value of the underlying real file system.
179     *
180     * @return the accuracy of the last modification time in milliseconds. A value of 0 means perfectly accurate,
181     *         anything {@literal > 0} might be off by this value. For example, sftp has an accuracy of 1000 ms.
182     */
183    double getLastModTimeAccuracy();
184}