Anonymous inner classes - PersistenceExceptionTypeNotPersistable

[rpx99]

Playing around with wicket and plugged in eclipse serializer.

Generally seems to work, but in wicket a lot of anonymous inner classes are used, e.g. for AjaxLinks.

That seems to be a problem for eclipse serializer (bit of a bummer).

Found some stack overflow posts:

Link 1

Link 2

According to the Features
anonymous inner classes
are supported.

But the exception says it's not:

Details: Synthetic classes ($1 etc.) are not reliably persistence since a simple reordering of source code elements would change the name identity of a class. For a type system that has to rely upon resolving types by their identifying name, this would silently cause a potentially fatal error. If handling synthetic classes (e.g. anonymous inner classes) is absolutely necessary, a custom one.microstream.persistence.types.PersistenceTypeResolver can be used to remove the exception and assume complete responsibility for correctly handling synthetic class names.

There seems to be the possibility to use the a custom type handler.

What about the solution mentioned in Link 2?
How do other serializers do it?

[hg-ms]

As the exception states, it is dangerous to serialize classes with compiler generated names.
If this is an acceptable risk, it might be simpler to replace the default PersistenceTypeResolver with a custom implementation that accepts enumerated classes names, instead of writing custom type handlers for all affected classes.

A draft of custom PersistenceTypeResolver may look like:

public class MyPersistenceTypeResolver implements PersistenceTypeResolver {

	@Override
	public String deriveTypeName(Class<?> type) {
		
		// handleable special case of sub-enum classes with enumerating class names.
		if(XReflect.isSubEnum(type))
		{
			return Persistence.derivePersistentTypeNameEnum(type, Persistence.substituteClassIdentifierSeparator());
		}

		// unhandleable general case of classes with enumerating class names.
		if(XReflect.hasEnumeratedTypeName(type))
		{
			//don't throw exception to allow enumerating class names.
			//see org.eclipse.serializer.persistence.types.Persistence.derivePersistentTypeName(Class<?>, String) for the original default logic 
		}

		// "normal" types without problematic enumerating class names.
		return type.getName();
	}
}

Set up a storage using a custom PersistenceTypeResolver:

EmbeddedStorageManager storage = EmbeddedStorage.Foundation(workdir)
	.onConnectionFoundation(cf -> cf.setTypeResolver(new MyPersistenceTypeResolver()))
	.start();

[rpx99]

Thank you, that is very helpful!

I understand that reordering is a problem because the positional index appends to the class name $1,$2,...

Do you think it is possible to create something like an AnonymousClassProcessor, which attaches a unique ID (e.g. a UUID) to anonymous classes and does compile time / bytecode manipulation so that the outcome are $UUID files?

E.g. Lombok generates lots of stuff like this?