is it possible to set custom metadata on files, using Java?

Question

Is it possible to get and set custom metadata on File instances? I want to use the files that I process through my system as some kind of a very simple database, where every fil

Answer 1

You should always check if the filesystem supports UserDefinedFileAttributeView for the specific file you want to set You can simply invoke this

Files.getFileStore(Paths.get(path_to_file))).supportsFileAttributeView(UserDefinedFileAttributeView.class);

From my experience, the UserDefinedFileAttributeView is not supported in FAT* and HFS+ (for MAC) filesystems

Answer 2

In java 7 you can do this using the Path class and UserDefinedFileAttributeView.

Here is the example taken from there:

A file's MIME type can be stored as a user-defined attribute by using this code snippet:

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

To read the MIME type attribute, you would use this code snippet:

Path file = ...;
UserDefinedFileAttributeView view = Files
.getFileAttributeView(file,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();