add custom attribute or metadata to file java

Question

I have files that need an extra attribute called "encryption used". But this gives "IllegalArgumentExeption". I know why it gives that error, "encryption used" isn't known as an attribute, but is there a way I can force it to be? Or add custom metadata to the file?

 Path path = new File("/propertyfiles/encdec.properties").toPath();

    try{
        Files.setAttribute(path, "encryption used", "testtesttest");
    }catch(IOException e){
        System.out.println(e.getMessage());
    }
    try{
        System.out.println(Files.getAttribute(path, "encryption used"));
    }catch(IOException e){
        System.out.println(e.getMessage());
    }

does this attribute mean that file encdec.properties is encryped? — Alexei Kaigorodov
– Alexei Kaigorodov, Commented Sep 23, 2013 at 9:25

Stephen C · Accepted Answer · 2023-03-30 14:50:05Z

14

If your file system supports user-defined (aka extended) attributes, then the way to set one would be like this:

Files.setAttribute(path, "user:encryption used", "testtesttest");

As the javadoc for setAttribute explains, the 2nd argument takes the form of an optional view-name and an attribute name. In this case, you need to use the UserDefinedFileAttributeView whose view-name is "user".

Note that different file system types support different attribute views, and your file system may not support this one. This particularly applies across different operating systems; e.g. you can't read a file's MacOS file attributes on a Linux system via these APIs.

edited Mar 30, 2023 at 14:50

answered Sep 23, 2013 at 9:25

Stephen C

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1 Comment

Thales Valias Over a year ago

Also, it's worth mentioning that extended attributes are platform dependent, so an attribute on a file created, let's say, on MacOS, cannot be read on Linux (at least not naturally)

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