RFR: 6450193: After the first Serialization, JTableHeader does not uninstall its UI

[Alexey Ivanov]

On Thu, 31 Aug 2023 08:02:35 GMT, Prasanta Sadhukhan <psadhukhan at openjdk.org> wrote:

> After the first time a JTableHeader is serialized, it no longer will uninstall its UI upon subsequent serializations.
> This happens for classes that use the BasicTableHeaderUI class. Any LAF that extends the BasicTableHeaderUI like SynthTableHeaderUI and WindowsTableHeaderUI will get an NotSerializableException thrown
> 
> Each time an JComponent instance is Serialized, a [counter ](https://github.com/openjdk/jdk/blob/218829e0a2a3ae5599b81733df53557966392033/src/java.desktop/share/classes/javax/swing/JComponent.java#L5644-L5645) for the instance is incremented. It is de-incremented in JComponent's writeObject or a class that implements it the same way, like JButton, JScrollPane etc..
> With JTableHeader it does not deincrement the counter. The uninstall mechanism will not uninstall a UI if the counter is not 0 on the first pass..It is not possible to call JComponent.setWriteObjectCounter in JTableHeader as it is not in the same package so the fix is to remove the writeObject implementation and rely on JComponent writeObject implementation to make sure uninstallation of UI happens and also NotSerializableException does not happen for Synth

Changes requested by aivanov (Reviewer).

test/jdk/javax/swing/JTableHeader/SerializeJTableHeader.java line 44:

> 42:         JTableHeader jth = new JTableHeader();
> 43:         try {
> 44:             for(int i = 0; i < 10; i ++){

Suggestion:

            for (int i = 0; i < 10; i ++) {

test/jdk/javax/swing/JTableHeader/SerializeJTableHeader.java line 46:

> 44:             for(int i = 0; i < 10; i ++){
> 45:                 ByteArrayOutputStream baos = new ByteArrayOutputStream();
> 46:                 ObjectOutputStream oos = new ObjectOutputStream(baos);

You should use try with resources to close the streams as a good pattern, even though closing byte-array does nothing, nor does it leak any resources.

test/jdk/javax/swing/JTableHeader/SerializeJTableHeader.java line 54:

> 52:         catch (Exception x) {
> 53:             x.printStackTrace();
> 54:         }

Shouldn't the test fail if an exception is thrown? Without the fix, `NotSerializableException` is expected, and the test will fail. But the test will never fail if you catch the exception to print a message.

Suggestion:

        } catch (Exception x) {
            x.printStackTrace();
        }

test/jdk/javax/swing/JTableHeader/SerializeJTableHeader.java line 68:

> 66:     }
> 67: 
> 68:     public static void main(String ... args) throws Exception{

Suggestion:

    public static void main(String... args) throws Exception {

There's usually no space before the ellipses.

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PR Review: https://git.openjdk.org/jdk/pull/15507#pullrequestreview-1620659017
PR Review Comment: https://git.openjdk.org/jdk/pull/15507#discussion_r1321963036
PR Review Comment: https://git.openjdk.org/jdk/pull/15507#discussion_r1321964990
PR Review Comment: https://git.openjdk.org/jdk/pull/15507#discussion_r1321967563
PR Review Comment: https://git.openjdk.org/jdk/pull/15507#discussion_r1321968570