RFR: 8347123: Add missing @serial tags to other modules

[Hannes Wallnöfer]

On Tue, 21 Jan 2025 19:41:39 GMT, Phil Race <prr at openjdk.org> wrote:

>> Please review a doc-only change to mostly add missing `@serial` javadoc tags. This is a sub-task of [JDK-8286931] to allow us to re-enable the javadoc `-serialwarn` option in the JDK doc build, which has been disabled since JDK 19.
>> 
>> [JDK-8286931]: https://bugs.openjdk.org/browse/JDK-8286931
>> 
>> For private and package-private serialized fields that already have a doc comment, the main description is converted to a block tag by prepending `@serial` since these fields do not require a main description. For protected and public serialized fields that require a main description, an empty `@serial` block tag is appended to the doc comment instead. The effect is the same, as the main description is used in `serial-form.html` if the `@serial` tag is missing or empty. For those fields that do not have a doc comment, a doc comment with an empty `@serial` tag is added. 
>> 
>> Apart from missing `@serial` tags, this PR also adds a `@serialData` tag to `java.awt.datatransfer.DataFlavor.writeExternal(ObjectOutput)` that the javadoc `-serialwarn` option complains about. This is the only change in this PR that adds documentation text and causes a change in the generated documentation.
>
> src/java.datatransfer/share/classes/java/awt/datatransfer/DataFlavor.java line 1288:
> 
>> 1286: 
>> 1287:     /**
>> 1288:      * Serializes this {@code DataFlavor}.
> 
> This most definitely changes the serialisation spec. So a CSR is needed.
> Also shouldn't readExternal be updated to correspond ?

Only the `writeExternal` method is required to have a `@serialData` tag in order to keep javadoc running with `-serialwarn` option from complaining. I guess the thinking is that the `readExternal` logic can be derived from that.

@prrace do you have any suggestions for the spec change, or are you ok with the proposed wording?

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PR Review Comment: https://git.openjdk.org/jdk/pull/22980#discussion_r1924979277