8225181: KeyStore should have a getAttributes method

Reviewed-by: mullan

src/java.base/share/classes/java/security/KeyStoreSpi.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 2021, 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
@@ -447,6 +447,33 @@ public abstract class KeyStoreSpi {
         return;
     }
 
+    /**
+     * Retrieves the attributes associated with the given alias.
+     *
+     * @implSpec
+     * The default implementation returns an empty {@code Set}.
+     * {@code KeyStoreSpi} implementations that support attributes
+     * should override this method.
+     *
+     * @param alias the alias name
+     * @return an unmodifiable {@code Set} of attributes. This set is
+     *      empty if the given alias does not exist or there are no
+     *      attributes associated with the alias. This set may also be
+     *      empty for {@code PrivateKeyEntry} or {@code SecretKeyEntry}
+     *      entries that contain protected attributes. These protected
+     *      attributes should be populated into the result returned by
+     *      {@link #engineGetEntry} and can be retrieved by calling
+     *      the {@link Entry#getAttributes} method.
+     *
+     * @throws KeyStoreException if the keystore has not been initialized
+     * (loaded).
+     *
+     * @since 18
+     */
+    public Set<Entry.Attribute> engineGetAttributes(String alias) {
+        return Collections.emptySet();
+    }
+
     /**
      * Gets a {@code KeyStore.Entry} for the specified alias
      * with the specified protection parameter.