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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      */
FileTypeMap()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      */
getContentType(File file)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      */
getContentType(String filename)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      */
setDefaultFileTypeMap(FileTypeMap fileTypeMap)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                 if (FileTypeMap.class.getClassLoader() == null ||
100                     FileTypeMap.class.getClassLoader() !=
101                         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      */
getDefaultFileTypeMap()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 }
133