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/*
 * 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;

import java.io.File;

/**
 * A file system, made up of a hierarchy of files.
 */
public interface FileSystem {
    /**
     * Returns the root file of this file system.
     *
     * @return The root FileObject.
     * @throws FileSystemException if an error occurs.
     */
    FileObject getRoot() throws FileSystemException;

    /**
     * Returns the name of the root file of this file system. The root name always contains a path String of "/".
     *
     * @return the root FileName.
     */
    FileName getRootName();

    /**
     * The root URI passed as a file system option or obtained from the rootName.
     *
     * @return The root URI.
     */
    String getRootURI();

    /**
     * Determines if this file system has a particular capability.
     * 

* TODO - Move this to another interface, so that set of capabilities can be queried. * * @param capability The capability to check for. * @return true if this filesystem has the requested capability. Note that not all files in the file system may have * the capability. */ boolean hasCapability(Capability capability); /** * Returns the parent layer if this is a layered file system. * * @return The parent layer, or null if this is not a layered file system. * @throws FileSystemException if an error occurs. */ FileObject getParentLayer() throws FileSystemException; /** * Gets the value of an attribute of the file system. *

* TODO - change to {@code Map getAttributes()} instead?
* TODO - define the standard attribute names, and define which attrs are guaranteed to be present. * * @param attrName The name of the attribute. * @return The value of the attribute. * @throws org.apache.commons.vfs2.FileSystemException If the file does not exist, or is being written, or if the * attribute is unknown. * @see org.apache.commons.vfs2.FileContent#getAttribute */ Object getAttribute(String attrName) throws FileSystemException; /** * Sets the value of an attribute of the file's content. Creates the file if it does not exist. * * @param attrName The name of the attribute. * @param value The value of the attribute. * @throws FileSystemException If the file is read-only, or is being read, or if the attribute is not supported, or * on error setting the attribute. * @see FileContent#setAttribute */ void setAttribute(String attrName, Object value) throws FileSystemException; /** * Finds a file in this file system. * * @param name The name of the file. * @return The file. Never returns null. * @throws FileSystemException if an error occurs. */ FileObject resolveFile(FileName name) throws FileSystemException; /** * Finds a file in this file system. * * @param name The name of the file. This must be an absolute path. * @return The file. Never returns null. * @throws FileSystemException if an error occurs. */ FileObject resolveFile(String name) throws FileSystemException; /** * Adds a listener on a file in this file system. * * @param file The file to attach the listener to. * @param listener The listener to add. */ void addListener(FileObject file, FileListener listener); /** * Removes a listener from a file in this file system. * * @param file The file to remove the listener from. * @param listener The listener to remove. */ void removeListener(FileObject file, FileListener listener); /** * Adds a junction to this file system. A junction is a link that attaches the supplied file to a point in this file * system, making it look like part of the file system. * * @param junctionPoint The point in this file system to add the junction. * @param targetFile The file to link to. * @throws FileSystemException If this file system does not support junctions, or the junction point or target file * is invalid (the file system may not support nested junctions, for example). */ void addJunction(String junctionPoint, FileObject targetFile) throws FileSystemException; /** * Removes a junction from this file system. * * @param junctionPoint The junction to remove. * @throws FileSystemException On error removing the junction. */ void removeJunction(String junctionPoint) throws FileSystemException; /** * Creates a temporary local copy of a file and its descendants. If this file is already a local file, a copy is not * made. *

* Note that the local copy may include additonal files, that were not selected by the given selector. *

* TODO - Add options to indicate whether the caller is happy to deal with extra files being present locally (eg if * the file has been replicated previously), or whether the caller expects only the selected files to be present. * * @param file The file to replicate. * @param selector The selector to use to select the files to replicate. * @return The local copy of this file. * @throws FileSystemException If this file does not exist, or on error replicating the file. */ File replicateFile(FileObject file, FileSelector selector) throws FileSystemException; /** * Returns the FileSystemOptions used to instantiate this filesystem. * * @return The FileSystemOptions. */ FileSystemOptions getFileSystemOptions(); /** * Returns a reference to the FileSytemManager. * * @return The FileSystemManager. */ FileSystemManager getFileSystemManager(); /** * Returns the accuracy of the last modification time. *

* The local file provider is not very smart in figuring this out, for remote access to file systems the providers * typically don't know the value of the underlying real file system. * * @return the accuracy of the last modification time in milliseconds. A value of 0 means perfectly accurate, * anything {@literal > 0} might be off by this value. For example, sftp has an accuracy of 1000 ms. */ double getLastModTimeAccuracy(); }





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