JDK 14 RFR of JDK-8202385: Annotation to mark serial-related fields and methods

Joe Darcy joe.darcy at oracle.com
Sat Jul 13 03:19:16 UTC 2019

Hi Roger,

On 7/12/2019 1:31 PM, Roger Riggs wrote:
> Hi Joe,
> As an annotation on a field or method, this is a use site annotation.

It is an annotation intended for the declarations of fields and methods 
of Serializable types.

> From the description, the checks that could be added would only be done
> if the annotation was present and the annotation is a tag for existing
> fields and methods that are part of the serialization spec.

Right; the annotation is semantically only applicable to the fields and 
methods associated with the serialization system.

> The signatures of the fields and methods can be known to the compiler 
> independent
> of the annotation and produce the same warnings.
> So this looks like a case of trying to have belt and suspenders.
> If the checks are not done when the annotation is not present, then it 
> will still be
> the case that incorrect or misused fields and methods will still 
> escape detection.
> Though the details of the compiler check are outside of the scope of 
> this annotation,
> it seems unclear whether the annotation is necessary.

I have a prototype annotation processor to implement checks for

     JDK-8202056: Expand serial warning to check for bad overloads of 
serial-related methods and ineffectual fields

The current version of the processor does not assume the presence of 
java.io.Serial. The summarize the existing checking methodology:

     If a type is Serialiazable and a field or method has a name 
matching the names of one of the special fields or methods to 
serialization, check that the field or method has the required 
modifiers, type, and, the the case of methods, parameter types and 
exception types.

That is all well and good and represents a large fraction of the 
checking of interest. However, it does not catch a mis-declaration like 
"readobject" instead of "readObject". One could argue that sufficiently 
thorough testing should catch that kind of error; however, my impression 
is that thoroughness of testing is rare in practice. I don't think it 
would be reasonable for javac to have some kind of Hamming distance 
(https://en.wikipedia.org/wiki/Hamming_distance) check between the name 
of fields/methods and the name of the serialization related fields 
methods to try to catch such mis-declarations. An annotation like 
java.io.Serial is intended to allow the programmer to indicate "yes, 
this is supposed to be one of the serialization related fields or 
methods" and enable the compile to perform checks against that category 
of error.

> Can the name of the annotation be more descriptive?
> Just "Serial" seems a bit too simple and does not have a strong 
> binding to the Serialization classes and specification.
> Alternatives:
>    SerialMetadata
>    SerialControl
>    SerialFunction

 From the earlier design iterations "Serial" was chosen to be evocative 
of the "@serial" javadoc tag.



> 39:  There should be a reference to the serialization specification 
> for the definition
> of the fields and methods to make it clear where the authoritative 
> identification is spec'd.
> 73-75:  Please align the <ul> and </ul> tags on separate lines with 
> matching indentation.
> 77: Extra leading space.
> Regards, Roger
> On 7/9/19 7:14 PM, Joe Darcy wrote:
>> Hello,
>> Returning to some old work [1], please review the addition of a 
>> java.io.Serial annotation type for JDK 14 to mark serial-related 
>> fields and methods:
>>     webrev: http://cr.openjdk.java.net/~darcy/8202385.3/
>>     CSR: https://bugs.openjdk.java.net/browse/JDK-8217698
>> Thanks,
>> -Joe
>> [1] Previous review threads:
>> http://mail.openjdk.java.net/pipermail/core-libs-dev/2018-May/053055.html 
>> http://mail.openjdk.java.net/pipermail/core-libs-dev/2018-August/054801.html 

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