<AWT Dev> [9] Review request for 8133453 Remove AWTKeyStroke.registerSubclass(Class) method

[Sergey Bylokhov]

Looks fine to me.

On 01.09.15 13:49, Alexander Scherbatiy wrote:
>
> Hello,
>
> Could you review the fix:
>    bug: https://bugs.openjdk.java.net/browse/JDK-8133453
>    webrev: http://cr.openjdk.java.net/~alexsch/8133453/webrev.00
>
>    The class KeyStroke has been added to the javax.swing package first
> and then copied to the java.awt.AWTKeyStroke class.
>    Most of KeyStroke class methods looks like registering KeyStroke
> class and call to the parent AWTKeyStroke method.
>
>    AWTKeyStroke class is intended to contain keyChar, keyCode,
> modifiers, and keyRelease flag and it seems
>    there are no reasons that this class can be subclassed.
>
>    The suggestion is to remove the AWTKeyStroke.registerSubclass(Class)
> method.
>
>    The AWTKeyStroke.registerSubclass(Class) method can be deprecated so
> only AWTKeyStroke and KeyStroke instances is allowed to be created.
>    The result will be that a user code get ClassCastException when
> casting a returned key stroke to the custom key stroke which has the
> similar effect.
>
>    Removing the method in question leads to the binary compatibility
> issue if someone uses the method. The following code will not work:
>    --------------------------
>      public class CustomKeyStroke extends AWTKeyStroke {
>
>          public static void registerCustomKeyStroke() {
>              AWTKeyStroke.registerSubclass(CustomKeyStroke.class); //
> removed method
>          }
>      }
>
>      CustomKeyStroke.registerCustomKeyStroke();
>      AWTKeyStroke keyStroke = AWTKeyStroke.getAWTKeyStroke('C');
>      CustomKeyStroke customKeyStroke = (CustomKeyStroke) keyStroke; //
> CustomKeyStroke instance is not returned
>    --------------------------
>
>    The proposed workaround is to use a map between unique AWTKeyStroke
> instances and custom key strokes:
>    --------------------------
>      private static HashMap<AWTKeyStroke, CustomKeyStroke> keyStrokeMap
> = new HashMap<>();
>
>      public static CustomKeyStroke getCustomKeyStroke(char c) {
>          AWTKeyStroke ketStroke = AWTKeyStroke.getAWTKeyStroke(c);
>          CustomKeyStroke customKeyStroke = keyStrokeMap.get(ketStroke);
>
>          if (customKeyStroke == null) {
>              customKeyStroke = new CustomKeyStroke(ketStroke);
>              keyStrokeMap.put(ketStroke, customKeyStroke);
>          }
>
>          return customKeyStroke;
>      }
>    --------------------------
>
>
>    AWT/Swing library only registers KeyStroke class
> (AWTKeyStroke.registerSubclass(KeyStroke.class) calls in the KeyStroke
> class)
>    and never registers AWTKeyStroke.class.
>    After the first KeyStroke.getKeyStroke(...) call in the keyStroke
> class only KeyStroke instances will be created by AWTKeyStroke.
>
>    The solution proposed in the fix is to always create
> javax.swing.KeyStroke instances.
>
> Thanks,
> Alexandr.
>


-- 
Best regards, Sergey.