Support Stream as mapper method return type

[quaff]

No description provided.

[harawata]

Hello @quaff ,

Thank you for the PR, but I don't think this is a good idea.

1. Users can easily create Stream in their own code after retrieving List or Cursor from MyBatis.
2. Users should be able to close Cursor at any point, but it's not possible if we return Stream wrapping Cursor.

I will close this as "won't fix".

[quaff]

Users can easily create Stream in their own code after retrieving List or Cursor from MyBatis.

Users would expect returning standard Stream instead of proprietary Cursor from declarative mapper interface, especially for beginner, they may don't even know Cursor, see GH-3213.

It's not so easily to create Stream from Cursor, Sure it's easily for List, but List is not suitable for large result, It may cause OOM issue.

It's more easily to create Optional in their own code, but MyBatis provide built-in supports, so I think Stream supports is reasonable, WDYT @harawata

[harawata]

Thanks for the comment, @quaff !

I'll reopen for other devs to comment.

Comparison with Optional is a fair point.
It's not obvious, however, that the returned Stream wraps Cursor which requires extra care (i.e. resultOrdered="true"), so I still prefer not to merge this personally.
And, in case other devs like this, I would request some additional documentation (please do not work on it yet. I don't want you to waste any time).

[quaff]

I'll reopen for other devs to comment.

Thanks for reconsideration. @harawata

It's not obvious, however, that the returned Stream wraps Cursor which requires extra care (i.e. resultOrdered="true").

I researched #2812 (comment), I don't think extra care required for resultOrdered="true", Stream inherit all features and limitations from Cursor, It doesn't introduce new things, correct me if I'm wrong.

[harawata]

What I meant was it is not clear to users that "Stream inherits all features and limitations from Cursor" and it requires additional documentation IF we merge this (again, please do not work on the doc update yet).

[MasatoshiTada]

Is there any progress on this PR? 👀
Stream is very useful for users as it allows for separation of concerns.
Since Cursor is a MyBatis-specific class, our code becomes dependent on MyBatis.
By using Stream, the dependency of our code on MyBatis is reduced.