Java compact1, compact2, compact3 java.nio.file.attribute Interface UserDefinedFileAttributeView（JDK8）

Method Detail

• name

  String name()

  Returns the name of this attribute view. Attribute views of this type have the name "user".

  Specified by:

  name in interface AttributeView

  Returns:

  the name of the attribute view

• list

  List<String> list()
             throws IOException

  Returns a list containing the names of the user-defined attributes.

  Returns:

  An unmodifiable list containing the names of the file's user-defined

  Throws:

  IOException - If an I/O error occurs

  SecurityException - In the case of the default provider, a security manager is installed, and it denies RuntimePermission("accessUserDefinedAttributes") or its checkRead method denies read access to the file.

• size

  int size(String name)
    throws IOException

  Returns the size of the value of a user-defined attribute.

  Parameters:

  name - The attribute name

  Returns:

  The size of the attribute value, in bytes.

  Throws:

  ArithmeticException - If the size of the attribute is larger than Integer.MAX_VALUE

  IOException - If an I/O error occurs

  SecurityException - In the case of the default provider, a security manager is installed, and it denies RuntimePermission("accessUserDefinedAttributes") or its checkRead method denies read access to the file.

• read

  int read(String name,
           ByteBuffer dst)
    throws IOException

  Read the value of a user-defined attribute into a buffer.

  This method reads the value of the attribute into the given buffer as a sequence of bytes, failing if the number of bytes remaining in the buffer is insufficient to read the complete attribute value. The number of bytes transferred into the buffer is n, where n is the size of the attribute value. The first byte in the sequence is at index p and the last byte is at index p + n - 1, where p is the buffer's position. Upon return the buffer's position will be equal to p + n; its limit will not have changed.

  Usage Example: Suppose we want to read a file's MIME type that is stored as a user-defined attribute with the name "user.mimetype".

      UserDefinedFileAttributeView view =
          Files.getFileAttributeView(path, UserDefinedFileAttributeView.class);
      String name = "user.mimetype";
      ByteBuffer buf = ByteBuffer.allocate(view.size(name));
      view.read(name, buf);
      buf.flip();
      String value = Charset.defaultCharset().decode(buf).toString();
   

  Parameters:

  name - The attribute name

  dst - The destination buffer

  Returns:

  The number of bytes read, possibly zero

  Throws:

  IllegalArgumentException - If the destination buffer is read-only

  IOException - If an I/O error occurs or there is insufficient space in the destination buffer for the attribute value

  SecurityException - In the case of the default provider, a security manager is installed, and it denies RuntimePermission("accessUserDefinedAttributes") or its checkRead method denies read access to the file.

  See Also:

  size(java.lang.String)

• write

  int write(String name,
            ByteBuffer src)
     throws IOException

  Writes the value of a user-defined attribute from a buffer.

  This method writes the value of the attribute from a given buffer as a sequence of bytes. The size of the value to transfer is r, where r is the number of bytes remaining in the buffer, that is src.remaining(). The sequence of bytes is transferred from the buffer starting at index p, where p is the buffer's position. Upon return, the buffer's position will be equal to p + n, where n is the number of bytes transferred; its limit will not have changed.

  If an attribute of the given name already exists then its value is replaced. If the attribute does not exist then it is created. If it implementation specific if a test to check for the existence of the attribute and the creation of attribute are atomic with respect to other file system activities.

  Where there is insufficient space to store the attribute, or the attribute name or value exceed an implementation specific maximum size then an IOException is thrown.

  Usage Example: Suppose we want to write a file's MIME type as a user-defined attribute:

      UserDefinedFileAttributeView view =
          FIles.getFileAttributeView(path, UserDefinedFileAttributeView.class);
      view.write("user.mimetype", Charset.defaultCharset().encode("text/html"));
   

  Parameters:

  name - The attribute name

  src - The buffer containing the attribute value

  Returns:

  The number of bytes written, possibly zero

  Throws:

  IOException - If an I/O error occurs

  SecurityException - In the case of the default provider, a security manager is installed, and it denies RuntimePermission("accessUserDefinedAttributes") or its checkWrite method denies write access to the file.

• delete

  void delete(String name)
       throws IOException

  Deletes a user-defined attribute.

  Parameters:

  name - The attribute name

  Throws:

  IOException - If an I/O error occurs or the attribute does not exist

  SecurityException - In the case of the default provider, a security manager is installed, and it denies RuntimePermission("accessUserDefinedAttributes") or its checkWrite method denies write access to the file.