1 /*
   2  * Copyright (c) 1997, 2014, 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 javax.activation;
  27 
  28 import java.io.File;
  29 import java.util.Map;
  30 import java.util.WeakHashMap;
  31 
  32 /**
  33  * The FileTypeMap is an abstract class that provides a data typing
  34  * interface for files. Implementations of this class will
  35  * implement the getContentType methods which will derive a content
  36  * type from a file name or a File object. FileTypeMaps could use any
  37  * scheme to determine the data type, from examining the file extension
  38  * of a file (like the MimetypesFileTypeMap) to opening the file and
  39  * trying to derive its type from the contents of the file. The
  40  * FileDataSource class uses the default FileTypeMap (a MimetypesFileTypeMap
  41  * unless changed) to determine the content type of files.
  42  *
  43  * @see javax.activation.FileTypeMap
  44  * @see javax.activation.FileDataSource
  45  * @see javax.activation.MimetypesFileTypeMap
  46  *
  47  * @since 1.6
  48  */
  49 
  50 public abstract class FileTypeMap {
  51 
  52     private static FileTypeMap defaultMap = null;
  53     private static Map<ClassLoader,FileTypeMap> map =
  54                                 new WeakHashMap<ClassLoader,FileTypeMap>();
  55 
  56     /**
  57      * The default constructor.
  58      */
  59     public FileTypeMap() {
  60         super();
  61     }
  62 
  63     /**
  64      * Return the type of the file object. This method should
  65      * always return a valid MIME type.
  66      *
  67      * @param file A file to be typed.
  68      * @return The content type.
  69      */
  70     abstract public String getContentType(File file);
  71 
  72     /**
  73      * Return the type of the file passed in.  This method should
  74      * always return a valid MIME type.
  75      *
  76      * @param filename the pathname of the file.
  77      * @return The content type.
  78      */
  79     abstract public String getContentType(String filename);
  80 
  81     /**
  82      * Sets the default FileTypeMap for the system. This instance
  83      * will be returned to callers of getDefaultFileTypeMap.
  84      *
  85      * @param fileTypeMap The FileTypeMap.
  86      * @exception SecurityException if the caller doesn't have permission
  87      *                                  to change the default
  88      */
  89     public static synchronized void setDefaultFileTypeMap(FileTypeMap fileTypeMap) {
  90         SecurityManager security = System.getSecurityManager();
  91         if (security != null) {
  92             try {
  93                 // if it's ok with the SecurityManager, it's ok with me...
  94                 security.checkSetFactory();
  95             } catch (SecurityException ex) {
  96                 // otherwise, we also allow it if this code and the
  97                 // factory come from the same (non-system) class loader (e.g.,
  98                 // the JAF classes were loaded with the applet classes).
  99                 ClassLoader cl = FileTypeMap.class.getClassLoader();
 100                 if (cl == null || cl.getParent() == null ||
 101                     cl != fileTypeMap.getClass().getClassLoader())
 102                     throw ex;
 103             }
 104         }
 105         // remove any per-thread-context-class-loader FileTypeMap
 106         map.remove(SecuritySupport.getContextClassLoader());
 107         defaultMap = fileTypeMap;
 108     }
 109 
 110     /**
 111      * Return the default FileTypeMap for the system.
 112      * If setDefaultFileTypeMap was called, return
 113      * that instance, otherwise return an instance of
 114      * <code>MimetypesFileTypeMap</code>.
 115      *
 116      * @return The default FileTypeMap
 117      * @see javax.activation.FileTypeMap#setDefaultFileTypeMap
 118      */
 119     public static synchronized FileTypeMap getDefaultFileTypeMap() {
 120         if (defaultMap != null)
 121             return defaultMap;
 122 
 123         // fetch per-thread-context-class-loader default
 124         ClassLoader tccl = SecuritySupport.getContextClassLoader();
 125         FileTypeMap def = map.get(tccl);
 126         if (def == null) {
 127             def = new MimetypesFileTypeMap();
 128             map.put(tccl, def);
 129         }
 130         return def;
 131     }
 132 }