8360887: (fs) Files.getFileAttributeView returns unusable FileAttributeView if UserDefinedFileAttributeView unavailable (aix)

Reviewed-by: mbaesken
Backport-of: 0572b6e

Author: TheRealMDoerr

src/java.base/aix/classes/sun/nio/fs/AixFileSystemProvider.java

@@ -1,6 +1,6 @@
 /*
  * Copyright (c) 2008, 2025, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2013 SAP SE. All rights reserved.
+ * Copyright (c) 2013, 2025 SAP SE. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -52,15 +52,24 @@ AixFileStore getFileStore(UnixPath path) throws IOException {
         return new AixFileStore(path);
     }
 
+    static boolean supportsUserDefinedFileAttributeView(Path obj) {
+        try {
+            FileStore store = Files.getFileStore(obj);
+            return store.supportsFileAttributeView(UserDefinedFileAttributeView.class);
+        } catch (IOException e) {
+            return false;
+        }
+    }
+
     @Override
     @SuppressWarnings("unchecked")
     public <V extends FileAttributeView> V getFileAttributeView(Path obj,
                                                                 Class<V> type,
                                                                 LinkOption... options)
     {
         if (type == UserDefinedFileAttributeView.class) {
-            return (V) new AixUserDefinedFileAttributeView(UnixPath.toUnixPath(obj),
-                    Util.followLinks(options));
+            return !supportsUserDefinedFileAttributeView(obj) ? null :
+                (V) new AixUserDefinedFileAttributeView(UnixPath.toUnixPath(obj), Util.followLinks(options));
         }
         return super.getFileAttributeView(obj, type, options);
     }
@@ -71,8 +80,8 @@ public DynamicFileAttributeView getFileAttributeView(Path obj,
                                                          LinkOption... options)
     {
         if (name.equals("user")) {
-            return new AixUserDefinedFileAttributeView(UnixPath.toUnixPath(obj),
-                    Util.followLinks(options));
+            return !supportsUserDefinedFileAttributeView(obj) ? null :
+                new AixUserDefinedFileAttributeView(UnixPath.toUnixPath(obj), Util.followLinks(options));
         }
         return super.getFileAttributeView(obj, name, options);
     }

test/jdk/java/nio/file/FileStore/Basic.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2008, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -22,7 +22,7 @@
  */
 
 /* @test
- * @bug 4313887 6873621 6979526 7006126 7020517 8264400
+ * @bug 4313887 6873621 6979526 7006126 7020517 8264400 8360887
  * @summary Unit test for java.nio.file.FileStore
  * @key intermittent
  * @library .. /test/lib
@@ -107,6 +107,12 @@ static void doTests(Path dir) throws IOException {
         assertTrue(store1.supportsFileAttributeView("user") ==
             store1.supportsFileAttributeView(UserDefinedFileAttributeView.class));
 
+        // check if getFileAttributeView behaves as specified if the user defined view is unsupported
+        if (!store1.supportsFileAttributeView(UserDefinedFileAttributeView.class) &&
+            Files.getFileAttributeView(dir, UserDefinedFileAttributeView.class) != null) {
+            throw new RuntimeException("UserDefinedFileAttributeView not supported, getFileAttributeView should return null");
+        }
+
         /**
          * Test: Space atributes
          */