1 /*
2 * Copyright 2007-2009 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package java.nio.file;
27
28 import java.nio.file.attribute.*;
29 import java.util.Map;
30 import java.io.InputStream;
31 import java.io.OutputStream;
32 import java.io.IOException;
33
34 /**
35 * A reference to a file.
36 *
37 * <p> A {@code FileRef} is an object that locates a file and defines methods to
38 * open the file for reading or writing. It also provides access to associated
39 * metadata or file attributes.
40 *
41 * @since 1.7
42 * @see java.nio.file.attribute.Attributes
43 * @see java.io.File#toPath
44 */
45
46 public interface FileRef {
47
48 /**
49 * Opens the file referenced by this object, returning an input stream to
50 * read from the file. The stream will not be buffered, and is not required
51 * to support the {@link InputStream#mark mark} or {@link InputStream#reset
52 * reset} methods. The stream will be safe for access by multiple concurrent
53 * threads. Reading commences at the beginning of the file.
54 *
55 * <p> The {@code options} parameter determines how the file is opened.
56 * If no options are present then it is equivalent to opening the file with
57 * the {@link StandardOpenOption#READ READ} option. In addition to the {@code
58 * READ} option, an implementation may also support additional implementation
59 * specific options.
60 *
61 * @return an input stream to read bytes from the file
62 *
63 * @throws IllegalArgumentException
64 * if an invalid combination of options is specified
65 * @throws UnsupportedOperationException
66 * if an unsupported option is specified
67 * @throws IOException
68 * if an I/O error occurs
69 * @throws SecurityException
70 * In the case of the default provider, and a security manager is
71 * installed, the {@link SecurityManager#checkRead(String) checkRead}
72 * method is invoked to check read access to the file.
73 */
74 InputStream newInputStream(OpenOption... options) throws IOException;
75
76 /**
77 * Opens or creates the file located by this object for writing, returning
78 * an output stream to write bytes to the file.
79 *
80 * <p> The {@code options} parameter determines how the file is opened.
81 * If no options are present then this method creates a new file for writing
82 * or truncates an existing file. In addition to the {@link StandardOpenOption
83 * standard} options, an implementation may also support additional
84 * implementation specific options.
85 *
86 * <p> The resulting stream will not be buffered. The stream will be safe
87 * for access by multiple concurrent threads.
88 *
89 * @param options
90 * options specifying how the file is opened
91 *
92 * @return a new output stream
93 *
94 * @throws IllegalArgumentException
95 * if {@code options} contains an invalid combination of options
96 * @throws UnsupportedOperationException
97 * if an unsupported option is specified
98 * @throws IOException
99 * if an I/O error occurs
100 * @throws SecurityException
101 * In the case of the default provider, and a security manager is
102 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
103 * method is invoked to check write access to the file.
104 */
105 OutputStream newOutputStream(OpenOption... options) throws IOException;
106
107 /**
108 * Returns a file attribute view of a given type.
109 *
110 * <p> A file attribute view provides a read-only or updatable view of a
111 * set of file attributes. This method is intended to be used where the file
112 * attribute view defines type-safe methods to read or update the file
113 * attributes. The {@code type} parameter is the type of the attribute view
114 * required and the method returns an instance of that type if supported.
115 * The {@link BasicFileAttributeView} type supports access to the basic
116 * attributes of a file. Invoking this method to select a file attribute
117 * view of that type will always return an instance of that class.
118 *
119 * <p> The {@code options} array may be used to indicate how symbolic links
120 * are handled by the resulting file attribute view for the case that the
121 * file is a symbolic link. By default, symbolic links are followed. If the
122 * option {@link LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} is present then
123 * symbolic links are not followed. This option is ignored by implementations
124 * that do not support symbolic links.
125 *
126 * @param type
127 * the {@code Class} object corresponding to the file attribute view
128 * @param options
129 * options indicating how symbolic links are handled
130 *
131 * @return a file attribute view of the specified type, or {@code null} if
132 * the attribute view type is not available
133 *
134 * @throws UnsupportedOperationException
135 * If options contains an unsupported option. This exception is
136 * specified to allow the {@code LinkOption} enum be extended
137 * in future releases.
138 *
139 * @see Attributes#readBasicFileAttributes
140 */
141 <V extends FileAttributeView> V getFileAttributeView(Class<V> type,
142 LinkOption... options);
143
144 /**
145 * Sets the value of a file attribute.
146 *
147 * <p> The {@code attribute} parameter identifies the attribute to be set
148 * and takes the form:
149 * <blockquote>
150 * [<i>view-name</i><b>:</b>]<i>attribute-name</i>
151 * </blockquote>
152 * where square brackets [...] delineate an optional component and the
153 * character {@code ':'} stands for itself.
154 *
155 * <p> <i>view-name</i> is the {@link FileAttributeView#name name} of a {@link
156 * FileAttributeView} that identifies a set of file attributes. If not
157 * specified then it defaults to {@code "basic"}, the name of the file
158 * attribute view that identifies the basic set of file attributes common to
159 * many file systems. <i>attribute-name</i> is the name of the attribute
160 * within the set.
161 *
162 * <p> <b>Usage Example:</b>
163 * Suppose we want to set the DOS "hidden" attribute:
164 * <pre>
165 * file.setAttribute("dos:hidden", true);
166 * </pre>
167 *
168 * @param attribute
169 * the attribute to set
170 * @param value
171 * the attribute value
172 * @param options
173 * options indicating how symbolic links are handled
174 *
175 * @throws UnsupportedOperationException
176 * if the attribute view is not available or it does not support
177 * updating the attribute
178 * @throws IllegalArgumentException
179 * if the attribute value is of the correct type but has an
180 * inappropriate value
181 * @throws ClassCastException
182 * If the attribute value is not of the expected type or is a
183 * collection containing elements that are not of the expected
184 * type
185 * @throws IOException
186 * If an I/O error occurs
187 * @throws SecurityException
188 * In the case of the default provider, and a security manager is
189 * installed, its {@link SecurityManager#checkWrite(String) checkWrite}
190 * method denies write access to the file. If this method is invoked
191 * to set security sensitive attributes then the security manager
192 * may be invoked to check for additional permissions.
193 */
194 void setAttribute(String attribute, Object value, LinkOption... options)
195 throws IOException;
196
197 /**
198 * Reads the value of a file attribute.
199 *
200 * <p> The {@code attribute} parameter identifies the attribute to be read
201 * and takes the form:
202 * <blockquote>
203 * [<i>view-name</i><b>:</b>]<i>attribute-name</i>
204 * </blockquote>
205 * where square brackets [...] delineate an optional component and the
206 * character {@code ':'} stands for itself.
207 *
208 * <p> <i>view-name</i> is the {@link FileAttributeView#name name} of a {@link
209 * FileAttributeView} that identifies a set of file attributes. If not
210 * specified then it defaults to {@code "basic"}, the name of the file
211 * attribute view that identifies the basic set of file attributes common to
212 * many file systems. <i>attribute-name</i> is the name of the attribute.
213 *
214 * <p> The {@code options} array may be used to indicate how symbolic links
215 * are handled for the case that the file is a symbolic link. By default,
216 * symbolic links are followed and the file attribute of the final target
217 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
218 * NOFOLLOW_LINKS} is present then symbolic links are not followed and so
219 * the method returns the file attribute of the symbolic link.
220 *
221 * <p> <b>Usage Example:</b>
222 * Suppose we require the user ID of the file owner on a system that
223 * supports a "{@code unix}" view:
224 * <pre>
225 * int uid = (Integer)file.getAttribute("unix:uid");
226 * </pre>
227 *
228 * @param attribute
229 * the attribute to read
230 * @param options
231 * options indicating how symbolic links are handled
232 * @return the attribute value or {@code null} if the attribute view
233 * is not available or it does not support reading the attribute
234 *
235 * reading the attribute
236 * @throws IOException
237 * if an I/O error occurs
238 * @throws SecurityException
239 * In the case of the default provider, and a security manager is
240 * installed, its {@link SecurityManager#checkRead(String) checkRead}
241 * method denies read access to the file. If this method is invoked
242 * to read security sensitive attributes then the security manager
243 * may be invoked to check for additional permissions.
244 */
245 Object getAttribute(String attribute, LinkOption... options) throws IOException;
246
247 /**
248 * Reads a set of file attributes as a bulk operation.
249 *
250 * <p> The {@code attributes} parameter identifies the attributes to be read
251 * and takes the form:
252 * <blockquote>
253 * [<i>view-name</i><b>:</b>]<i>attribute-list</i>
254 * </blockquote>
255 * where square brackets [...] delineate an optional component and the
256 * character {@code ':'} stands for itself.
257 *
258 * <p> <i>view-name</i> is the {@link FileAttributeView#name name} of a {@link
259 * FileAttributeView} that identifies a set of file attributes. If not
260 * specified then it defaults to {@code "basic"}, the name of the file
261 * attribute view that identifies the basic set of file attributes common to
262 * many file systems.
263 *
264 * <p> The <i>attribute-list</i> component is a comma separated list of
265 * zero or more names of attributes to read. If the list contains the value
266 * {@code "*"} then all attributes are read. Attributes that are not supported
267 * are ignored and will not be present in the returned map. It is
268 * implementation specific if all attributes are read as an atomic operation
269 * with respect to other file system operations.
270 *
271 * <p> The following examples demonstrate possible values for the {@code
272 * attributes} parameter:
273 *
274 * <blockquote>
275 * <table border="0">
276 * <tr>
277 * <td> {@code "*"} </td>
278 * <td> Read all {@link BasicFileAttributes basic-file-attributes}. </td>
279 * </tr>
280 * <tr>
281 * <td> {@code "size,lastModifiedTime,lastAccessTime"} </td>
282 * <td> Reads the file size, last modified time, and last access time
283 * attributes. </td>
284 * </tr>
285 * <tr>
286 * <td> {@code "posix:*"} </td>
287 * <td> Read all {@link PosixFileAttributes POSIX-file-attributes}.. </td>
288 * </tr>
289 * <tr>
290 * <td> {@code "posix:permissions,owner,size"} </td>
291 * <td> Reads the POSX file permissions, owner, and file size. </td>
292 * </tr>
293 * </table>
294 * </blockquote>
295 *
296 * <p> The {@code options} array may be used to indicate how symbolic links
297 * are handled for the case that the file is a symbolic link. By default,
298 * symbolic links are followed and the file attribute of the final target
299 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
300 * NOFOLLOW_LINKS} is present then symbolic links are not followed and so
301 * the method returns the file attribute of the symbolic link.
302 *
303 * @param attributes
304 * The attributes to read
305 * @param options
306 * Options indicating how symbolic links are handled
307 *
308 * @return A map of the attributes returned; may be empty. The map's keys
309 * are the attribute names, its values are the attribute values
310 *
311 * @throws IOException
312 * If an I/O error occurs
313 * @throws SecurityException
314 * In the case of the default provider, and a security manager is
315 * installed, its {@link SecurityManager#checkRead(String) checkRead}
316 * method denies read access to the file. If this method is invoked
317 * to read security sensitive attributes then the security manager
318 * may be invoke to check for additional permissions.
319 */
320 Map<String,?> readAttributes(String attributes, LinkOption... options)
321 throws IOException;
322 }