Hi Phil,
On 9/22/2019 1:25 PM, Philip Race wrote:
+ @SuppressWarnings("serial") // Not statically typed as Serializable
So is the comment being used to distinguish this overloading of what
"serial" means ? Why not introduce a new warning category ?
The -Xlint:serial check in javac has had an operational meaning of "does
a serializable type define a serialVersionUID?" The work-in-progress is
aiming to expand this to cover other aspect of declaring serializable
(and externalizable) types.
It would be possible to put the new checks in their own category, but
that would limit their use and some of new checks find what are most
likely semantic errors, such as declaring a serialVersionUID in an enum
type, which gets silently ignored.
Randomly looking at
====
src/java.desktop/share/classes/java/awt/Container.java
@@ -3849,10 +3849,11 @@
/**
* The handler to fire {@code PropertyChange}
* when children are added or removed
*/
+ @SuppressWarnings("serial") // Not statically typed as
Serializable
protected ContainerListener accessibleContainerHandler = null;
===
I see that Container has a writeObject method which doesn't write this
field, so it is effectively transient.
I recognise that it is difficult for the compiler to figure this out,
so perhaps there should just be a policy
not to check classes that have writeObject methods ?
Yes, it is not feasible for this level of analysis to decode the
semantics of writeObject and related methods. The analysis does skip
over classes using serialPersistentFields, which is an alternative
mechanism to indicate which fields are used for serialization.
In terms of possible false positives, I think it is acceptable to keep
doing the checks in the presence of a writeObject method since a
writeObject can be used to make alterations to serialization process
other than changing the set of fields written out.
Also in such a case, would it be an effectively compatible change to
add transient to the field, so that
it presumably would no longer need this warning.
And the class does define a serialVersionUID so adding transient to the
field should preserve serial compatibility.
I haven't looked but presumably there could be other such cases.
Will you be filing bugs for all the fixable cases ?
Someone should ;-)
To make sure my intentions are clear, nothing in this overall cleanup
effort should be construed as seeking to assume ownership of all the
serialization in the JDK. The primary ownership will remain with the
component team in question. The new checks are meant to the an aid,
especially to writing new serializable types, while also prompting some
examination of the existing types in an effort to allow the warning to
enabled by default in the build.
Thanks,
-Joe
-phil
On 9/21/19, 12:48 PM, Joe Darcy wrote:
Hello,
Quick background, I'm working on expanding the compile-time
serialization checks of javac's -Xlint:serial option. Ahead of that
work going back, I'm analyzing the JDK sources and plan to
pre-suppress the coming-soon new warnings, fixing or at least filing
follow-up bugs for any problems that are found. Corresponding
suppression bugs are already out for review against core libs
(JDK-8231202) and security libs (JDK-8231262).
The new check in development is if a serializable class has an
instance field that is not declared to be a serializable type. This
might actually be fine in practice, such as if the field in question
always points to a serializable object at runtime, but it is arguably
worth noting as an item of potential concern. This check is skipped
if the class using the serialPersistentFields mechanism.
For the client libs, the webrev with the new @SuppressedWarnings
annotations is:
JDK-8231334: Suppress warnings on non-serializable instance
fields in client libs serializable classes
http://cr.openjdk.java.net/~darcy/8231334.0/
The changes are mostly in awt, but also some in beans, a few in
printing, and one in sound.
As discussed with Phil off-line, the new checks also found an
existing known issue, the auxiliary class java.awt.ImageMediaEntry
declared in MediaTracker.java is not serializable/deserializable in
practice (JDK-4397681).
Thanks,
-Joe
