CODEWITHSUNDEEP
spring-mvcjacksonkotlin
Paul Holt
Paul Holt

Reputation: 51

Why does Kotlin with Spring MVC JSON return an empty object?

I've been playing with server side Kotlin, Spring MVC and Jackson. I built a simple application using http://start.spring.io/, but I might have made a mistake in the JsonView annotation.

This:

@RestController

class MyRestController {
    @RequestMapping("/user")
    @JsonView(User::class)
    fun getUser() : User = User("Fred",50)
}

data class User(val name: String, val age: Int)

...when called with curl

ph@sleek ~ $ curl -X GET http://localhost:8080/user; echo
{}
ph@sleek ~ $

...the result is {} when I expected {"name":"Fred","age":50}. Is there something I did wrong?

Upvotes: 2

Views: 1212

Answers (2)

julo
julo

Reputation: 121

if you do want to use @JsonView (which is necessary in many scenarios), I was running into the same empty object problem until I added the jackson-module-kotlin dependency to my project.

compile 'com.fasterxml.jackson.module:jackson-module-kotlin'

See here: https://stackoverflow.com/a/48019143/5258628

Upvotes: 1

Paul Holt
Paul Holt

Reputation: 51

Much simpler than I thought. After finding that Jackson was able to serialise the object just fine, I started making adjustments, and found the default was better than configuration:

class MyRestController {
    @RequestMapping("/user")
    fun getUser() : User = User("Fred",50)
}

Perfect:

ph@sleek ~ $ curl -X GET http://localhost:8080/user; echo
{"name":"Fred","age":50}

Upvotes: 1

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