Initial draft of MongoDB Document API support

[mp911de]

This pull request introduces Document API support for MongoDB (see #2215) as additional implementation, without changing DBObject support.

Morphia is entirely based on DBObject. Tests are a bit of a mixture of objects and Documents right now. Happy to dive into a discussion.

[mp911de]

There's a split between some base functionality and the actual execution to enable different execution models (async, reactive) to be built on top of AbstractMongodbQuery.

[Shredder121]

Just wanted to mention, looks nice so far.
👀

So what would you recommend with the split of execution modes? How would you see the reactive mongodbquery work?

[mp911de]

The main issue to tackle is query execution required for joins/relations. Since RxJava 1 is EOL, the only reactive driver is the Reactive Streams one. Maybe we could introduce something like continuations that are agnostic in regard to the underlying execution model.

This increases complexity in general but could be a nice approach to support both execution models from a single base class.

The idea is to introduce something like callback interfaces along the desired operation/criteria to query on a particular collection.

[odrotbohm]

Hey guys, any chance we can get some feedback on your plans going forward? The MongoDB Java driver team has indicated that it plans to remove the deprecated DBObject based APIs in some future version and we don't want to end up with the Spring Data Querydsl support ending up broken in a driver release.

I wouldn't mind getting the support for the new APIs introduced in a parallel type hierarchy so that we can move Spring Data over to the new APIs.

[Shredder121]

I myself am not well-versed in the world of reactive programming, so maybe you, @mp911de can maintain the mongodb subproject once it's in the mainline? I don't know if it's something you are able/willing to do?

[odrotbohm]

We're not talking anything reactive here but the fact that the MongoDB Java driver switched from using DBObject to Document for its synchronous operations a while ago.

[mp911de]

This pull request does not contain any reactive bits. However, there's a split between base functionality and the actual class which executes the query to not make assumptions about the execution model within basic query creation functionality.

[Shredder121]

We're not talking anything reactive here

Oh, sorry. In that case I wouldn't mind migrating to Document exclusively, for Querydsl 5.
Unless you want both DBObject and Document support for now? Or both in Querydsl 4 and 5 respectively?

This pull request does not contain any reactive bits. However, there's a split between base functionality and the actual class which executes the query to not make assumptions about the execution model within basic query creation functionality.

EDIT: saw Mark's comment just now, yes I know about the split, but I'd rather you take a bit of responsibility, so you can get the mongodb submodule (and with assist also core) up to spec for later having reactive queries.

Then I think the process can be a bit more sped up, since I've been really busy lately, as you probably noticed.

[jwgmeligmeyling]

@odrotbohm @mp911de Is this PR actually sufficient to port Spring Data over to the new API already? Or is this really still the initial draft?

Our current set of maintainers has little experience or ongoing work with MongoDB, so it is hard for me to review this properly. I am very willing to integrate it though if it helps you forward and helps the overall compatibility with DBObject being deprecated.

That said, what do you think about bumping the dependency versions of the MongoDB driver and/or Morphia (see #2029)? Which version is Spring Data currently targetting?

[mp911de]

Let me have a look and potentially rebase the code. MongoDB 4.1 is btw. the most recent version. Spring Data MongoDB 3.1 (to be released in late October) is targeting the MongoDB 4.1 driver.

I will leave a comment with further details once I had a look.

[jwgmeligmeyling]

Great, thanks! Lets finally get this out of the way after 2 years 😉

[mp911de]

Meh! I've deleted my repository in the meantime and so this PR base got lost. I suggest creating a new PR from https://github.com/mp911de/querydsl/tree/issue/mongodb-document-api and closing this one. We fixed a few issues in Spring Data (we've inlined the Querydsl code) and the new PR would include also the fixes.

[mp911de]

Closing in favor of #2689.