Support java.util.Optional as return type of mapper method

[kazuki43zoo]

I know this fix is ad hoc. However, i want to provide early this feature for Java 8 users. I will improve this feature at 3.5 or later version.

This fix allow following method definition:

public interface UserMapper {

  @Select("select * from users where id = #{id}")
  Optional<User> findOne(Integer id);

}

Please review.

[harawata]

Hi,

I wrote a patch to support Optional, a while ago.
Here's the branch...
https://github.com/harawata/mybatis-3/commits/optional
... and test cases.
https://github.com/harawata/mybatis-optional-test

I consider it is still under the committers' review (@eddumelendez seemed to like it), but I would appreciate if you could check it out and let me know what you think.

Thank you,
Iwao

[kazuki43zoo]

Hi @harawata, it's great !! I will confirm your patch at later and leave comments if needed.

Thanks !

[harawata]

Hi @kazuki43zoo ,

Do you mind if I add some commits to this PR?

[harawata]

@kazuki43zoo , I have added a few commits (hope it was OK!).

@jeffgbutler @christianpoitras
It is very simple, but satisfies the minimum requirement we discussed on #228 , I think.
Please take a look when you have time.

To reduce the noise, it's better to add w=1 when reviewing the diff.
https://github.com/mybatis/mybatis-3/pull/799/files?w=1

[kazuki43zoo]

@harawata Thanks for your improvements. I feel your changes are good!

[alexhilman]

Hello, I'm curious: is there a timeline for the acceptance and release of this pull request?

[christianpoitras]

All changes seem fine. @harawata, you can merge the pull request.

[harawata]

Thanks @christianpoitras !
I will merge it as soon as we release 3.4.6 .

[alexhilman]

Thanks @christianpoitras and @harawata - I am looking forward to using it.