Spring boot isn't serializing kotlin class - spring

Question

I'm trying to build a simple api with spring boot and kotlin. When I make a request to save a new user everything goes well, a new user is persisted, but response body is empty. I don't know why, I return the new user. Please help me to understand why Jackson isn't serializing my kotlin class.
I can assure that the user returned is not null.
Entity:
#Entity
data class User(#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private val id: Long = 0L,
private var createdAt: LocalDateTime = LocalDateTime.now(),
private var enabled: Boolean = false,
private val username: String = "",
private val password: String = "",
private val name: String = "") {
#PrePersist
private fun onCreate() {
this.enabled = true
this.createdAt = LocalDateTime.now();
}
}
Controller:
#RestController
#RequestMapping("users")
class UserController {
#Autowired
private lateinit var userService: UserService
#PostMapping
fun save(#RequestBody user: User): User {
return this.userService.save(user)
}
}
build.gradle:
buildscript {
ext {
kotlinVersion = '1.2.20'
springBootVersion = '2.0.0.RC1'
}
repositories {
mavenCentral()
maven { url "https://repo.spring.io/snapshot" }
maven { url "https://repo.spring.io/milestone" }
}
dependencies {
classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
classpath("org.jetbrains.kotlin:kotlin-gradle-plugin:${kotlinVersion}")
classpath("org.jetbrains.kotlin:kotlin-allopen:${kotlinVersion}")
}
}
apply plugin: 'kotlin'
apply plugin: 'kotlin-spring'
apply plugin: 'eclipse'
apply plugin: 'org.springframework.boot'
apply plugin: 'io.spring.dependency-management'
group = 'br.com'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = 1.8
compileKotlin {
kotlinOptions {
freeCompilerArgs = ["-Xjsr305=strict"]
jvmTarget = "1.8"
}
}
compileTestKotlin {
kotlinOptions {
freeCompilerArgs = ["-Xjsr305=strict"]
jvmTarget = "1.8"
}
}
repositories {
mavenCentral()
maven { url "https://repo.spring.io/snapshot" }
maven { url "https://repo.spring.io/milestone" }
}
dependencies {
compile('org.springframework.boot:spring-boot-starter-data-jpa')
compile('org.springframework.boot:spring-boot-starter-web')
compile("org.jetbrains.kotlin:kotlin-stdlib-jdk8")
compile("org.jetbrains.kotlin:kotlin-reflect")
//JACKSON
compile "com.fasterxml.jackson.core:jackson-annotations"
compile "com.fasterxml.jackson.core:jackson-core"
compile "com.fasterxml.jackson.core:jackson-databind"
runtime "com.fasterxml.jackson.datatype:jackson-datatype-jdk8"
runtime "com.fasterxml.jackson.datatype:jackson-datatype-jsr310"
runtime "com.fasterxml.jackson.module:jackson-module-kotlin"
runtime('mysql:mysql-connector-java')
runtime('org.springframework.boot:spring-boot-devtools')
testCompile('org.springframework.boot:spring-boot-starter-test')
}
application.properties
#DATA SOURCE
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.url=jdbc\:mysql\://localhost:3307/kotlin-library
spring.datasource.username = root
spring.datasource.password =
#JPA
spring.jpa.database-platform=org.hibernate.dialect.MySQL5InnoDBDialect
spring.jpa.show-sql=true
spring.jpa.hibernate.ddl-auto=update
#SERVER
server.servlet.context-path=/
#JACKSON
spring.jackson.serialization.indent-output=true
spring.jackson.serialization.write-dates-as-timestamps=false
spring.jackson.serialization.write-durations-as-timestamps=false

Answer 1

Everything in your data class is private. Typically serialization ignores private members in a class. If you make the necessary fields you desire to get serialized public, or just remove the private keyword I'm betting it works for you.