Provide better integration & docs (for manual joins)

[pmaedel]

I successfully integrated joins manually with data r2dbc while utilizing the r2dbc mapping and have a couple of issues I would like to discuss.

Please see the example project here

1. It should be documented that R2dbcConverter must be obtained through ReactiveDataAccessStrategy
The docs state that R2dbcConverter is recommended to do most of the work. R2dbcConverter however must be obtained via ReactiveDataAccessStrategy. This is fine, but should be documented, as I did expect R2dbcConverter to be readily available as a Bean when being so heavily advertised.

2. R2dbcConverter should provide read functionality that accepts alias prefixes for columns
Please see this example.
I can easily map the root entity (tree) via read(type, row, rowMetadata). Mapping the aliased joined entity (fruit) however seems only to be possible by hacking a customized read functionality, which would better be provided via R2dbcConverter. I have seen that prefixes are available internally but could not find a way to use them for my use case.

3. Spring Data Repository Customization override priority is not working as documented
The docs state that Custom implementations have a higher priority than the base implementation and repository aspects. This ordering lets you override base repository and aspect methods and resolves ambiguity if two fragments contribute the same method signature.. This test shows, that overrides only occur when the parameter type of the override is made available to the custom implementation via generics. A matching signature without generics does not result in an override.

4. Please find out whether a separate persistence constructor is really necessary when using transient fields (with default values) in Kotlin data classes
Here I made the joined Entity available as a transient field. The necessity to provide a separate persistence constructor seems odd to me, as I would think it should be possible to exclude a @Transient field during mapping for which default value is defined?

[mp911de]

Care to carve out each item into its own issue? Otherwise, it will be next to impossible to have an ordered discussion.

[pmaedel]

Sure, maybe you could give me a pointer into which projects the separate issues should be (re)created?

[mp911de]

This is already the right project for 1, 2, and 4. 3. can go to Stack Overflow as this is a good question to be shared with the community.

Please make sure to attach a bit of code to the tickets as external links can easily point to 404's and so the context of a ticket gets lost.

[pmaedel]

#447
#448
#449

https://stackoverflow.com/questions/63779752/spring-data-custom-repository-override-priority-is-not-working-as-documented