Custom deserializer of inlined value class (with delegate) about jackson-module-kotlin

[k163377]

I do not plan to implement setter support for value class at this time.
The reasons are as follows

• Requires a very complex implementation.
• It would degrade the overall performance of the kotlin-module as more reflection processing would be required.
• Deserialization of Kotlin classes is generally done using constructors or factory functions, and there is theoretically no case where you must always use setters.

So, I am inlining a class that just contains an int (this improves performance and memory allocation in my application).

I would suggest benchmarking first.
For libraries using kotlin-reflect, performance will degrade if you use the value class.
Compared to using data class, for example, the throughput of deserialization is roughly 70% (see the benchmark results in the link).
https://github.com/FasterXML/jackson-module-kotlin/blob/2.18/docs/value-class-support.md#note-on-the-use-of-value-class

[Bixilon]

Requires a very complex implementation.

Yes, agreed. I thought that is something already.

I would suggest benchmarking first.

My application does not use jackson heavily, it is more something for reading and writing settings (and a couple of other things). The main improvement comes from memory allocation, the color class is not mutable, and I already started replacing colors with int in a lot of places. The memory allocation goes down by 30-50 MB/s, it makes the gc almost sleep. In my case the jackson sacrifize would be totally worth it (even if it is slower by 10 times) to make the code quality go up and not use ints in the code. But I guess this is only true in my case and a lot of people would not want to take this.

Thanks for the answer, I need to find a different way (maybe use a color wrapper class or so for config files).

[k163377]

The main improvement comes from memory allocation

Hmmm, if that is the case, it might be preferable not to use jackson-module-kotlin.
I haven't done a comparison, but as far as I know, this module uses more memory because it uses kotlin-reflect.

If you are looking for performance, since Jackson supports record classes, you might consider defining DTO as JvmRecord and not using kotlinModule.
Alternatively, kotlinx-serialization does not use reflection, which may also reduce runtime memory consumption (I believe value class is also supported).