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package javax.activation;
import java.io.File;
import java.util.Map;
import java.util.WeakHashMap;
The FileTypeMap is an abstract class that provides a data typing
interface for files. Implementations of this class will
implement the getContentType methods which will derive a content
type from a file name or a File object. FileTypeMaps could use any
scheme to determine the data type, from examining the file extension
of a file (like the MimetypesFileTypeMap) to opening the file and
trying to derive its type from the contents of the file. The
FileDataSource class uses the default FileTypeMap (a MimetypesFileTypeMap
unless changed) to determine the content type of files.
See Also: - FileTypeMap
- FileDataSource
- MimetypesFileTypeMap
Since: 1.6
/**
* The FileTypeMap is an abstract class that provides a data typing
* interface for files. Implementations of this class will
* implement the getContentType methods which will derive a content
* type from a file name or a File object. FileTypeMaps could use any
* scheme to determine the data type, from examining the file extension
* of a file (like the MimetypesFileTypeMap) to opening the file and
* trying to derive its type from the contents of the file. The
* FileDataSource class uses the default FileTypeMap (a MimetypesFileTypeMap
* unless changed) to determine the content type of files.
*
* @see javax.activation.FileTypeMap
* @see javax.activation.FileDataSource
* @see javax.activation.MimetypesFileTypeMap
*
* @since 1.6
*/
public abstract class FileTypeMap {
private static FileTypeMap defaultMap = null;
private static Map<ClassLoader,FileTypeMap> map =
new WeakHashMap<ClassLoader,FileTypeMap>();
The default constructor.
/**
* The default constructor.
*/
public FileTypeMap() {
super();
}
Return the type of the file object. This method should
always return a valid MIME type.
Params: - file – A file to be typed.
Returns: The content type.
/**
* Return the type of the file object. This method should
* always return a valid MIME type.
*
* @param file A file to be typed.
* @return The content type.
*/
abstract public String getContentType(File file);
Return the type of the file passed in. This method should
always return a valid MIME type.
Params: - filename – the pathname of the file.
Returns: The content type.
/**
* Return the type of the file passed in. This method should
* always return a valid MIME type.
*
* @param filename the pathname of the file.
* @return The content type.
*/
abstract public String getContentType(String filename);
Sets the default FileTypeMap for the system. This instance
will be returned to callers of getDefaultFileTypeMap.
Params: - fileTypeMap – The FileTypeMap.
Throws: - SecurityException – if the caller doesn't have permission
to change the default
/**
* Sets the default FileTypeMap for the system. This instance
* will be returned to callers of getDefaultFileTypeMap.
*
* @param fileTypeMap The FileTypeMap.
* @exception SecurityException if the caller doesn't have permission
* to change the default
*/
public static synchronized void setDefaultFileTypeMap(FileTypeMap fileTypeMap) {
SecurityManager security = System.getSecurityManager();
if (security != null) {
try {
// if it's ok with the SecurityManager, it's ok with me...
security.checkSetFactory();
} catch (SecurityException ex) {
// otherwise, we also allow it if this code and the
// factory come from the same (non-system) class loader (e.g.,
// the JAF classes were loaded with the applet classes).
ClassLoader cl = FileTypeMap.class.getClassLoader();
if (cl == null || cl.getParent() == null ||
cl != fileTypeMap.getClass().getClassLoader())
throw ex;
}
}
// remove any per-thread-context-class-loader FileTypeMap
map.remove(SecuritySupport.getContextClassLoader());
defaultMap = fileTypeMap;
}
Return the default FileTypeMap for the system.
If setDefaultFileTypeMap was called, return
that instance, otherwise return an instance of
MimetypesFileTypeMap.
See Also: Returns: The default FileTypeMap
/**
* Return the default FileTypeMap for the system.
* If setDefaultFileTypeMap was called, return
* that instance, otherwise return an instance of
* <code>MimetypesFileTypeMap</code>.
*
* @return The default FileTypeMap
* @see javax.activation.FileTypeMap#setDefaultFileTypeMap
*/
public static synchronized FileTypeMap getDefaultFileTypeMap() {
if (defaultMap != null)
return defaultMap;
// fetch per-thread-context-class-loader default
ClassLoader tccl = SecuritySupport.getContextClassLoader();
FileTypeMap def = map.get(tccl);
if (def == null) {
def = new MimetypesFileTypeMap();
map.put(tccl, def);
}
return def;
}
}