Hi Roger,
Revised webev
http://cr.openjdk.java.net/~darcy/8202385.5/
Diff of last two versions below. To ease review, I elected not to reflow
the paragraphs at this time to reduce the number of lines of differences
between the two versions.
Several platform annotation types start there javadoc with
"Indicates..." so I kept that pattern.
It is true the serialization-defined fields and methods are accessed
reflectively and may not be otherwise accessed. That seems more relevant
to emphasize in the serialization spec itself, but it may be helpful to
note here so I added one as requested.
Cheers,
-Joe
31c31
< * Indicates that a field or method is related to the {@linkplain
---
> * Indicates that an annotated field or method is part of the {@linkplain
37c37,40
< * validate method overriding.
---
> * validate method overriding. {@code Serializable} classes are
encouraged to
> * use <code>@Serial</code> annotations to help a compiler catch
> * mis-declared serialization-related fields and methods,
> * mis-declarations that my otherwise be difficult to detect.
39c42
< * <p>Specifically, annotations of this type are intended to be
---
> * <p>Specifically, annotations of this type should be
59c62
< * A compiler can validate that a method or field marked with a
---
> * Compilers are encouraged to validate that a method or field marked
with a
61c64,65
< * methods or fields declared in a meaningful context.
---
> * methods or fields declared in a meaningful context and issue a warning
> * if that is not the case.
86a91,94
> *
> * Note that serialization mechanism accesses its designated fields
> * and methods reflectively and those fields and methods may appear
> * otherwise unused in a {@code Serializable} class.
On 8/1/2019 2:40 PM, Roger Riggs wrote:
Hi Joe,
It would be good to more closely define the semantics of the @Serial
annotation.
Suggestion for the first sentence:
"@Serial annotates each field or method specified by the <cite>Java
Object Serialization Specification</cite> of a {@linkplain
Serializable serializable} class."
This annotation type is intended to allow compile-time checking of
serialization-related declarations, analogous to the checking enabled
by the {@link java.lang.Override} annotation type to validate method
overriding.
It would be useful to describe that reflection is used to access and
use the fields and methods and they may otherwise appear to be unused.
A recommendation could be added in an @impleNote to apply @Serial to
each serialization defined method or field.
$02, Roger
On 7/13/19 1:16 PM, Joe Darcy wrote:
PS I've uploaded an updated an iteration of the webrev
http://cr.openjdk.java.net/~darcy/8202385.4/
to address. the syntactic concerns previously raised. I added
...defined by the <cite>Java Object Serialization
Specification</cite>...
which is the current name of the document and is similar to the style
of reference made in java.io.Serializable. Offhand, I didn't know of
the correct idiom to refer to the document as a working hyperlink,
but would be switch to that idiom.
Cheers,
-Joe
On 7/12/2019 8:19 PM, Joe Darcy wrote:
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.
Thanks,
-Joe
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
