ADDITIONAL SYSTEM INFORMATION :
FreeBSD 13.2
OpenJDK 17.0.8

A DESCRIPTION OF THE PROBLEM :
UserDefinedFileAttributeView::list() incorrectly always returns an empty list even if there are xattr.


A possible reason is that the UnixUserDefinedFileAttributeView assumes that the return value of UnixNativeDispatcher::flistxattr is a list of NULL-terminated C strings. This is true on macOS but not FreeBSD.

FreeBSD extattr_list_file() encodes Strings differently, without any \0 characters:
"""
extattr_list_file() returns a list of attributes present in the requested
     namespace. Each list entry consists of a single byte containing the
     length of the attribute name, followed by the attribute name. The attri-
     bute name is not terminated by ASCII 0 (nul).
"""

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the sample code below

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
[x]
1
(tested on macOS)
ACTUAL -
[]
1
(when running on FreeBSD)

---------- BEGIN SOURCE ----------
import static java.nio.charset.StandardCharsets.*;

import java.io.File;
import java.nio.file.Files;
import java.nio.file.attribute.UserDefinedFileAttributeView;

public class Main {

public static void main(String[] args) throws Exception {
File f = new File("test.txt");
f.createNewFile();

UserDefinedFileAttributeView xattr = Files.getFileAttributeView(f.toPath(), UserDefinedFileAttributeView.class);
xattr.write("x", UTF_8.encode("1"));
System.out.println(xattr.list());
System.out.println(xattr.size("x"));
}

}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Use lsextattr command and parse the output.

FREQUENCY : always