|
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.attribute; |
|
27 |
|
28 import java.nio.file.*; |
|
29 import java.util.Set; |
|
30 import java.io.IOException; |
|
31 |
|
32 /** |
|
33 * A file attribute view that provides a view of the file attributes commonly |
|
34 * associated with files on file systems used by operating systems that implement |
|
35 * the Portable Operating System Interface (POSIX) family of standards. |
|
36 * |
|
37 * <p> Operating systems that implement the <a href="http://www.opengroup.org"> |
|
38 * POSIX</a> family of standards commonly use file systems that have a |
|
39 * file <em>owner</em>, <em>group-owner</em>, and related <em>access |
|
40 * permissions</em>. This file attribute view provides read and write access |
|
41 * to these attributes. |
|
42 * |
|
43 * <p> The {@link #readAttributes() readAttributes} method is used to read the |
|
44 * file's attributes. The file {@link PosixFileAttributes#owner() owner} is |
|
45 * represented by a {@link UserPrincipal} that is the identity of the file owner |
|
46 * for the purposes of access control. The {@link PosixFileAttributes#group() |
|
47 * group-owner}, represented by a {@link GroupPrincipal}, is the identity of the |
|
48 * group owner, where a group is an identity created for administrative purposes |
|
49 * so as to determine the access rights for the members of the group. |
|
50 * |
|
51 * <p> The {@link PosixFileAttributes#permissions() permissions} attribute is a |
|
52 * set of access permissions. This file attribute view provides access to the nine |
|
53 * permission defined by the {@link PosixFilePermission} class. |
|
54 * These nine permission bits determine the <em>read</em>, <em>write</em>, and |
|
55 * <em>execute</em> access for the file owner, group, and others (others |
|
56 * meaning identities other than the owner and members of the group). Some |
|
57 * operating systems and file systems may provide additional permission bits |
|
58 * but access to these other bits is not defined by this class in this release. |
|
59 * |
|
60 * <p> <b>Usage Example:</b> |
|
61 * Suppose we need to print out the owner and access permissions of a file: |
|
62 * <pre> |
|
63 * FileRef file = ... |
|
64 * PosixFileAttributes attrs = file.newFileAttributeView(PosixFileAttributeView.class) |
|
65 * .readAttributes(); |
|
66 * System.out.format("%s %s%n", |
|
67 * attrs.owner().getName(), |
|
68 * PosixFilePermissions.toString(attrs.permissions())); |
|
69 * </pre> |
|
70 * |
|
71 * <h4> Dynamic Access </h4> |
|
72 * <p> Where dynamic access to file attributes is required, the attributes |
|
73 * supported by this attribute view are as defined by {@link |
|
74 * BasicFileAttributeView} and {@link FileOwnerAttributeView}, and in addition, |
|
75 * the following attributes are supported: |
|
76 * <blockquote> |
|
77 * <table border="1" cellpadding="8"> |
|
78 * <tr> |
|
79 * <th> Name </th> |
|
80 * <th> Type </th> |
|
81 * </tr> |
|
82 * <tr> |
|
83 * <td> "permissions" </td> |
|
84 * <td> {@link Set}<{@link PosixFilePermission}> </td> |
|
85 * </tr> |
|
86 * <tr> |
|
87 * <td> "group" </td> |
|
88 * <td> {@link GroupPrincipal} </td> |
|
89 * </tr> |
|
90 * </table> |
|
91 * </blockquote> |
|
92 * |
|
93 * <p> The {@link #getAttribute getAttribute} or {@link |
|
94 * #readAttributes(String,String[]) readAttributes(String,String[])} methods may |
|
95 * be used to read any of these attributes, or any of the attributes defined by |
|
96 * {@link BasicFileAttributeView} as if by invoking the {@link #readAttributes |
|
97 * readAttributes()} method. |
|
98 * |
|
99 * <p> The {@link #setAttribute setAttribute} method may be used to update the |
|
100 * file's last modified time, last access time or create time attributes as |
|
101 * defined by {@link BasicFileAttributeView}. It may also be used to update |
|
102 * the permissions, owner, or group-owner as if by invoking the {@link |
|
103 * #setPermissions setPermissions}, {@link #setOwner setOwner}, and {@link |
|
104 * #setGroup setGroup} methods respectively. |
|
105 * |
|
106 * <h4> Setting Initial Permissions </h4> |
|
107 * <p> Implementations supporting this attribute view may also support setting |
|
108 * the initial permissions when creating a file or directory. The |
|
109 * initial permissions are provided to the {@link Path#createFile createFile} |
|
110 * or {@link Path#createDirectory createDirectory} methods as a {@link |
|
111 * FileAttribute} with {@link FileAttribute#name name} {@code "posix:permissions"} |
|
112 * and a {@link FileAttribute#value value} that is the set of permissions. The |
|
113 * following example uses the {@link PosixFilePermissions#asFileAttribute |
|
114 * asFileAttribute} method to construct a {@code FileAttribute} when creating a |
|
115 * file: |
|
116 * |
|
117 * <pre> |
|
118 * Path path = ... |
|
119 * Set<PosixFilePermission> perms = |
|
120 * EnumSet.of(OWNER_READ, OWNER_WRITE, OWNER_EXECUTE, GROUP_READ); |
|
121 * path.createFile(PosixFilePermissions.asFileAttribute(perms)); |
|
122 * </pre> |
|
123 * |
|
124 * <p> When the access permissions are set at file creation time then the actual |
|
125 * value of the permissions may differ that the value of the attribute object. |
|
126 * The reasons for this are implementation specific. On UNIX systems, for |
|
127 * example, a process has a <em>umask</em> that impacts the permission bits |
|
128 * of newly created files. Where an implementation supports the setting of |
|
129 * the access permissions, and the underlying file system supports access |
|
130 * permissions, then it is required that the value of the actual access |
|
131 * permissions will be equal or less than the value of the attribute |
|
132 * provided to the {@link java.nio.file.Path#createFile createFile} or |
|
133 * {@link java.nio.file.Path#createDirectory createDirectory} methods. In |
|
134 * other words, the file may be more secure than requested. |
|
135 * |
|
136 * @since 1.7 |
|
137 * |
|
138 * @see Attributes#readPosixFileAttributes |
|
139 */ |
|
140 |
|
141 public interface PosixFileAttributeView |
|
142 extends BasicFileAttributeView, FileOwnerAttributeView |
|
143 { |
|
144 /** |
|
145 * Returns the name of the attribute view. Attribute views of this type |
|
146 * have the name {@code "posix"}. |
|
147 */ |
|
148 @Override |
|
149 String name(); |
|
150 |
|
151 /** |
|
152 * @throws IOException {@inheritDoc} |
|
153 * @throws SecurityException |
|
154 * In the case of the default provider, a security manager is |
|
155 * installed, and it denies {@link RuntimePermission}<tt>("accessUserInformation")</tt> |
|
156 * or its {@link SecurityManager#checkRead(String) checkRead} method |
|
157 * denies read access to the file. |
|
158 */ |
|
159 @Override |
|
160 PosixFileAttributes readAttributes() throws IOException; |
|
161 |
|
162 /** |
|
163 * Updates the file permissions. |
|
164 * |
|
165 * @param perms |
|
166 * The new set of permissions |
|
167 * |
|
168 * @throws ClassCastException |
|
169 * If the sets contains elements that are not of type {@code |
|
170 * PosixFilePermission} |
|
171 * @throws IOException |
|
172 * If an I/O error occurs |
|
173 * @throws SecurityException |
|
174 * In the case of the default provider, a security manager is |
|
175 * installed, and it denies {@link RuntimePermission}<tt>("accessUserInformation")</tt> |
|
176 * or its {@link SecurityManager#checkWrite(String) checkWrite} |
|
177 * method denies write access to the file. |
|
178 */ |
|
179 void setPermissions(Set<PosixFilePermission> perms) throws IOException; |
|
180 |
|
181 /** |
|
182 * Updates the file group-owner. |
|
183 * |
|
184 * @param group |
|
185 * The new file group-owner |
|
186 |
|
187 * @throws IOException |
|
188 * If an I/O error occurs |
|
189 * @throws SecurityException |
|
190 * In the case of the default provider, and a security manager is |
|
191 * installed, it denies {@link RuntimePermission}<tt>("accessUserInformation")</tt> |
|
192 * or its {@link SecurityManager#checkWrite(String) checkWrite} |
|
193 * method denies write access to the file. |
|
194 */ |
|
195 void setGroup(GroupPrincipal group) throws IOException; |
|
196 } |