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kotlinlang

So I realized I am not actually getting JSON in the `@PostMapping` so it won't use Jackson at all. Can Spring bind form data to Kotlin data class?

```
@PostMapping(value = ["/upload"], produces = arrayOf("application/json;charset=UTF-8"))
    @ResponseBody
    fun uploadStlFile(
            @RequestParam(required = true) file: MultipartFile
    )
```

your endpoint consumes files, mine:
```
consumes = MediaType.APPLICATION_FORM_URLENCODED_VALUE
```

I think you will be able to handle form data with spring :smiley: if its possible to handle files with miltipart

I don't think so..
In this example it works when `PersonDTO` is a java class but not when it is a Kotlin data class
```
@PostMapping(value = "/submit", consumes = MediaType.APPLICATION_FORM_URLENCODED_VALUE)
public String submit(PersonDTO data)
```

Kotlin data classes must have all fields populated once construction is done

but if you provide default values to your fields and make those fields `var`, you might make some headway

I’m imagining that Spring is trying to create an instance of your DTO, and then call the appropriate setters on the fields it has found

so I’m imagining your PersonDTO might look like:
```
data class PersonDTO (
    val firstName: String,
    val lastName: String,
    val email: String
)
```

but what you might need is something like:
```
data class PersonDTO (
    var firstName: String = "",
    var lastName: String = "",
    var email: String = ""
)
```

this way, PersonDTO has a default constructor, and you can set the field values post-construction

I think you are exactly right except one there is one problem:

I don't like mutable Kotlin data classes. :smile:

I think you can make a workaround for that with kotlin-reflect and everything

I know I did something similar for data classes and Spring Data

<https://kotlinlang.org/docs/reference/compiler-plugins.html#no-arg-compiler-plugin>

so yeah - I use this so that I can instantiate `@Entity` data classes with a no-arg constructor

what you could do is create a marker interface like `interface DTO` and then have `@DTO data class PersonDTO`

seems like an extra step and feels very much like Guice

but that’s not to say it’s a bad practice or anything