1 /*
2 * Copyright (c) 2007, 2009, Oracle and/or its affiliates. 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. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.nio.file.spi;
27
28 import java.nio.file.Path;
29 import java.io.IOException;
30
31 /**
32 * A file type detector for probing a file to guess its file type.
33 *
34 * <p> A file type detector is a concrete implementation of this class, has a
35 * zero-argument constructor, and implements the abstract methods specified
36 * below.
37 *
38 * <p> The means by which a file type detector determines the file type is
39 * highly implementation specific. A simple implementation might examine the
40 * <em>file extension</em> (a convention used in some platforms) and map it to
41 * a file type. In other cases, the file type may be stored as a file <a
42 * href="../attribute/package-summary.html"> attribute</a> or the bytes in a
43 * file may be examined to guess its file type.
44 *
45 * @see java.nio.file.Files#probeContentType(Path)
46 *
47 * @since 1.7
48 */
49
50 public abstract class FileTypeDetector {
51
52 private static Void checkPermission() {
53 SecurityManager sm = System.getSecurityManager();
54 if (sm != null)
55 sm.checkPermission(new RuntimePermission("fileTypeDetector"));
56 return null;
57 }
58 private FileTypeDetector(Void ignore) { }
59
60 /**
61 * Initializes a new instance of this class.
62 *
63 * @throws SecurityException
64 * If a security manager has been installed and it denies
65 * {@link RuntimePermission}<tt>("fileTypeDetector")</tt>
66 */
67 protected FileTypeDetector() {
68 this(checkPermission());
69 }
70
71 /**
72 * Probes the given file to guess its content type.
73 *
74 * <p> The means by which this method determines the file type is highly
75 * implementation specific. It may simply examine the file name, it may use
76 * a file <a href="../attribute/package-summary.html">attribute</a>,
77 * or it may examines bytes in the file.
78 *
79 * <p> The probe result is the string form of the value of a
80 * Multipurpose Internet Mail Extension (MIME) content type as
81 * defined by <a href="http://www.ietf.org/rfc/rfc2045.txt"><i>RFC 2045:
82 * Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet
83 * Message Bodies</i></a>. The string must be parsable according to the
84 * grammar in the RFC 2045.
85 *
86 * @param path
87 * the path to the file to probe
88 *
89 * @return The content type or {@code null} if the file type is not
90 * recognized
91 *
92 * @throws IOException
93 * An I/O error occurs
94 * @throws SecurityException
95 * If the implementation requires to access the file, and a
96 * security manager is installed, and it denies an unspecified
97 * permission required by a file system provider implementation.
98 * If the file reference is associated with the default file system
99 * provider then the {@link SecurityManager#checkRead(String)} method
100 * is invoked to check read access to the file.
101 *
102 * @see java.nio.file.Files#probeContentType
103 */
104 public abstract String probeContentType(Path path)
105 throws IOException;
106 }