Initial JDK 11 RFR of JDK-8202385: Annotation to mark serial-related fields and methods

[joe darcy]

Hello,

Please review the webrev (code below) to address

     JDK-8202385: Annotation to mark serial-related fields and methods
     http://cr.openjdk.java.net/~darcy/8202385.0/

The proposed java.io.Serial annotation type is intended to be used along 
with an augmented implementation of javac's "serial" lint check; that 
work will be done separately as part of JDK-8202056: "Expand serial 
warning to check for bad overloads of serial-related methods".

Currently, javac's serial lint check looks for serialVersionUID fields 
to be declared in Serializable classes. However, there are various other 
structural properties of the declaration of serialization-related fields 
and methods that could be checked at compile-time. The proposed 
java.io.Serial annotation type (name subject to change [*]) explicitly 
marks fields and methods that are intended to be called as part of the 
Serialization machinery. This marking allows using the wrong name for a 
method or field to be easily caught; the serialization mechanism will 
generally silently ignore mis-declared serialization-related fields and 
methods.

Since the annotation is intended for compile-time checking, the 
annotation type has has source retention, like the Override annotation type.

Cheers,

-Joe

[*] Unleash the bikes from the bikeshed! On the name and package of the 
annotation type, since the other serialization types are in the java.io 
package and the checks are not proposed to be part of the language, this 
annotation type more appropriately lives in java.io package rather than 
java.lang. The name "Serial" is consistent with the "@serial" javadoc 
tag. Other possible names include "Serialize" and "SerialRelated". 
Another possibility would be to have the annotation type be a nested 
type in java.io.Serializable.

-=-=-=-=-=-=-

// GPLv2 elided.

package java.io;

import java.lang.annotation.*;

/**
  * Indicates that a field or method is related to the {@linkplain
  * Serializable serialization mechanism}. 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.
  *
  * <p>Specifically, annotations of this type are intended to be
  * applied to serialization-related methods and fields in classes
  * declared to be {@code Serializable}. The five serialization-related
  * methods are:
  *
  * <ul>
  * <li>{@code private void writeObject(java.io.ObjectOutputStream 
stream) throws IOException}
  * <li>{@code private void readObject(java.io.ObjectInputStream stream) 
throws IOException, ClassNotFoundException}
  * <li>{@code private void readObjectNoData() throws ObjectStreamException}
  * <li><i>ANY-ACCESS-MODIFIER</i> {@code Object writeReplace() throws 
ObjectStreamException}
  * <li><i>ANY-ACCESS-MODIFIER</i> {@code Object readResolve() throws 
ObjectStreamException}
  * </ul>
  *
  * The two serialization-related fields are:
  *
  * <ul>
  * <li>{@code private static final ObjectStreamField[] 
serialPersistentFields}
  * <li>{@code private static final long serialVersionUID}
  * </ul>
  *
  * A compiler can validate that a method or field marked with a
  * <code>@Serial</code> annotation is one of the defined 
serialization-related
  * methods declared in a meaningful context.
  *
  * <p>It is a semantic error to apply this annotation to other fields 
or methods, including:
  * <ul>
  * <li>fields or methods in a class that is not {@code Serializable}
  *
  * <li>fields or methods of the proper structural declaration, but in
  * a type where they are ineffectual. For example, {@code enum} types
  * are defined to have a {@code serialVersionUID} of {@code 0L} so a
  * {@code serialVersionUID} field declared in an {@code enum} type is
  * ignored. The five serialization-related methods identified above
  * are likewise ignored for an {@code enum} type.
  *
  * </ul>
  */
@Target({ElementType.METHOD, ElementType.FIELD})
@Retention(RetentionPolicy.SOURCE)
public @interface Serial {
}