This is an interesting question.
In general, I don't think schema inference can handle these generics today.
Right now the SchemaRegistry is keyed off of Java class, and due to type
erasure all different instances of . MyClass<T> will look the same.
Now it might be possible to include generic type parameters in the
registry. You would not be able to use the @DefaultSchema annotation to
infer a schema, but you might be able to dynamically register a schema
using a TypeDescriptor. Unfortunately I think this would only sometimes
work. e..g. my experience has been that given a type T you can often figure
out T using reflection, but if there are nested types (e.g. List<T>) than
Java doesn't always preserve these types for introspection..
In sum, I think we could do a bit better for these types of classes, but
not a whole lot better.
Reuven
On Mon, Feb 4, 2019 at 6:02 AM Jeff Klukas <jklu...@mozilla.com> wrote:
> I've started experimenting with Beam schemas in the context of creating
> custom AutoValue-based classes and using AutoValueSchema to generate
> schemas and thus coders.
>
> AFAICT, schemas need to have types fully specified, so it doesn't appear
> to be possible to define an AutoValue class with a type parameter and then
> create a schema for it. Basically, I want to confirm whether the following
> type would ever be possible to create a schema for:
>
> @DefaultSchema(AutoValueSchema.class)
> @AutoValue
> public abstract class MyClass<T> {
> public abstract T getField1();
> public abstract String getField2();
> public static <T> MyClass<T> of(T field1, String field2) {
> return new AutoValue_MyClass(field1, field2);
> }
> }
>
> This may be an entirely reasonable limitation of the schema machinery, but
> I want to make sure I'm not missing something.
>
