Hi Reuven,
That's a great improvement for user.
I don't see an easy way to have annotation about side input/output.
I think we can also plan some extension annotation about schema. Like
@Element(schema = foo) in addition of the type. Thoughts ?
Regards
JB
On 04/06/2018 16:06, Reuven Lax wrote:
> Beam was created with an annotation-based processing API, that allows
> the framework to automatically inject parameters to a DoFn's process
> method (and also allows the user to mark any method as the process
> method using @ProcessElement). However, these annotations were never
> completed. A specific set of parameters could be injected (e.g. the
> window or PipelineOptions), but for anything else you had to access it
> through the ProcessContext. This limited the readability advantage of
> this API.
>
> A couple of months ago I spent a bit of time extending the set of
> annotations allowed. In particular, the most common uses of
> ProcessContext were accessing the input element and outputting elements,
> and both of those can now be done without ProcessContext. Example usage:
>
> new DoFn<InputT, OutputT>() {
> @ProcessElement process(@Element InputT element,
> OutputReceiver<OutputT> out) {
> out.output(convertInputToOutput(element));
> }
> }
>
> No need for ProcessContext anywhere in this DoFn! The Beam framework
> also does type checking - if the @Element type was not InputT, you would
> have seen an error. Multi-output DoFns also work, using a
> MultiOutputReceiver interface.
>
> I'll update the Beam docs later with this information, but most
> information accessible from ProcessContext, OnTimerContext,
> StartBundleContext, or FinishBundleContext can now be accessed via this
> sort of injection. The main exceptions are side inputs and output from
> finishbundle, both of which still require the context objects; however I
> hope to find time to provide direct access to those as well.
>
> pr/5331 (in progress) converts most of Beam's built-in transforms to use
> this clearer style.
>
> Reuven
--
Jean-Baptiste Onofré
jbono...@apache.org
http://blog.nanthrax.net
Talend - http://www.talend.com
