MongoDB: Towards Alpakka 1.0

[2m]

Fixes

Fixes #1082

Purpose

Adds javadsl for API parity.

Background Context

To reuse the implementation, MongoDB connector was switched from scala MongoDB driver to the Reactive Streams one.

BSON construction API can still be used from the scala driver, but that jar will need to be pulled in separately, as it is done in tests.

Missing

• doc updates
• javadsl sink tests

[2m]

Added missing Java tests and documentation updates.

[ennru]

A few questions about the API.

[ennru]

LGTM. Great to get a Java API!

[iozozturk]

Hi @ennru and @2m , I just realised that with this PR you removed all my work from original MongoDB connector and replaced it with some other library implementation. You guys opened the issue #1082 and without getting any reviews, @2m deleted whole implementation and replaced it and @ennru accepted the PR again without getting any community views. You didn't even mentioned or tag people to get notice. Why would I contribute anything if you are going to remove it in future at will?

Congrats! Decent community work!

[seglo]

This was before my time, but I believe the intention was only to re-use new functionality that was available in the upstream Mongo driver that I assume wasn't available when the connector was first implemented/donated to Alpakka.

Since using the reactivestreams implementation significantly reduced the surface area of this connector it was easier to bring the Java DSL up to par at the same time, which is a requirement of all Alpakka connectors so they can be used by the Java community at large with the same features as the Scala community.

I'm certain there was no ill will about the original implementation!

[ennru]

Hi @iozozturk
Sorry if we didn't live up to the expectations you have for how open source should be managed.
We are still grateful that you kicked off the Alpakka MongoDB connector back in 2017 with #148. As reported in #494 there was no API for Java users and our ambition is to offer somewhat similar APIs for both Scala and Java.
So for Alpakka 1.0 we wanted to have the Java DSL as #1082 stated in July 2018. We've seen very little community engagement around Alpakka MongoDB (which I believe is partly due to ReactiveMongo being a great choice for Scala users) so that's why @2m as member of Lightbend's Alpakka team implemented it in February 2019 on top of the Reactive Streams compatible MongoDB driver.
It was never the intention to remove the code you contributed, this was just a step to make Alpakka MongoDB attractive for more users.
Sorry, that we did not explicitly reached out to you when we worked on this.