1 /* 2 * Copyright (c) 2007, 2011, 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 } 107
