RFR: 8333796: Add missing serialization functionality to sun.reflect.ReflectionFactory

[David M. Lloyd]

On Fri, 28 Jun 2024 22:03:36 GMT, ExE Boss <duke at openjdk.org> wrote:

>> Issue [JDK-8164908](https://bugs.openjdk.org/browse/JDK-8164908) added support for functionality required to continue to support IIOP and custom serializers in light of additional module-based restrictions on reflection. It was expected that these libraries would use `sun.misc.Unsafe` in order to access fields of serializable classes. However, with JEP 471, the methods necessary to do this are being removed.
>> 
>> To allow these libraries to continue to function, it is proposed to add two methods to `sun.reflect.ReflectionFactory` which will allow serialization libraries to acquire a method handle to generated `readObject`/`writeObject` methods which set or get the fields of the serializable class using the serialization `GetField`/`PutField` mechanism. These generated methods should be used by serialization libraries to serialize and deserialize classes which do not have a `readObject`/`writeObject` method or which use `ObjectInputStream.defaultReadObject`/`ObjectOutputStream.defaultWriteObject` to supplement default serialization.
>> 
>> It is also proposed to add methods which allow for the reading of serialization-specific private static final fields from classes which have them.
>> 
>> With the addition of these methods, serialization libraries no longer need to rely on `Unsafe` for serialization/deserialization activities.
>> cc: @AlanBateman
>
> src/java.base/share/classes/jdk/internal/reflect/SerializationBytecodeGenerator.java line 239:
> 
>> 237: 
>> 238:     private static final ClassDesc CD_Generated_writeObject = ClassDesc.of("jdk.internal.reflect", "Generated$$writeObject");
>> 239:     private static final ClassDesc CD_Genearted_readObject = ClassDesc.of("jdk.internal.reflect", "Generated$$readObject");
> 
> It might be better to use `ReferenceClassDescImpl​.ofValidated​(String)` here, or at least `ClassDesc​.ofDescriptor​(String)` to avoid binary to internal name conversion:
> 
> Suggestion:
> 
>     private static final ClassDesc CD_ObjectInputStream = ReferenceClassDescImpl.ofValidated("Ljava/io/ObjectInputStream;");
>     private static final ClassDesc CD_ObjectInputStream_GetField = ReferenceClassDescImpl.ofValidated("Ljava/io/ObjectInputStream$GetField;");
> 
>     private static final ClassDesc CD_ObjectOutputStream = ReferenceClassDescImpl.ofValidated("Ljava/io/ObjectOutputStream;");
>     private static final ClassDesc CD_ObjectOutputStream_PutField = ReferenceClassDescImpl.ofValidated("Ljava/io/ObjectOutputStream$PutField;");
> 
>     private static final ClassDesc CD_Generated_writeObject = ReferenceClassDescImpl.ofValidated("Ljdk/internal/reflect/Generated$$writeObject;");
>     private static final ClassDesc CD_Generated_readObject = ReferenceClassDescImpl.ofValidated("Ljdk/internal/reflect/Generated$$readObject;");

Good idea.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19702#discussion_r1660974461