Bad Request with 400 status code in Spring boot

Question

Recently I am using Spring boot framework with Kotlin. Every thing is all okey with GET method. But when registering a new user with POST method I go faced some problem having Bad Request with status code 400. Here is my code associate with my spring boot project

User.kt

@Entity
@Table(name = "user_info")
data class User(
    @Id
    @SequenceGenerator(
        name = "user_seq",
        sequenceName = "user_seq",
        allocationSize = 1
    )
    @GeneratedValue(
        strategy = SEQUENCE,
        generator = "user_seq"
    )
    @Column(
        name = "id",
        updatable = false
    )
    val id: Long = -1,

    @Column(
        name = "first_name",
        nullable = false,
        length = 50,
        updatable = true
    )
    val firstName: String,

    @Column(
        name = "last_name",
        nullable = false,
        length = 50,
        updatable = true
    )
    val lastName: String,

    @Column(
        name = "email",
        nullable = true,
        length = 150,
        updatable = true
    )
    val email: String,

    @Column(
        name = "gender",
        nullable = false,
        length = 2,
        updatable = true
    )
    val gender: String,

    @Column(
        name = "date_of_birth",
        nullable = false,
        updatable = true
    )
    val dateOfBirth: LocalDate,

    @Column(
        name = "country",
        nullable = false,
        length = 50,
        updatable = true
    )
    val country: String
)

UserController.kt

@RestController
@RequestMapping(
    path = [
        "/api/v1/"
    ]
)
class UserController(
    @Autowired private val userService: UserService
) {

    @PostMapping("register")
    fun registerUser(@RequestBody user: User) {
        userService.registerUser(user)
    }

    @GetMapping("users")
    fun getUsers(): List<User> {
        return userService.getUsers()
    }

    @GetMapping("user/{id}")
    fun getUsers(@PathVariable("id") id: Long): User {
        return userService.getUserInfo(id)
    }
}

My Request Payload is

POST http://localhost:8080/api/v1/register
Content-Type: application/json

{
    "first_name" : "Abid",
    "last_name" : "Affan",
    "email" : "[email protected]",
    "gender" : "M",
    "date_of_birth" : "2019-05-03",
    "country" : "Bangladesh"
}

and my response payload is

POST http://localhost:8080/api/v1/register

HTTP/1.1 400 
Content-Type: application/json
Transfer-Encoding: chunked
Date: Mon, 01 Mar 2021 05:52:03 GMT
Connection: close

{
  "timestamp": "2021-03-01T05:52:03.634+00:00",
  "status": 400,
  "error": "Bad Request",
  "message": ""JSON parse error: Instantiation of [simple type, class com.example.demo.user.User] value failed for JSON property firstName due to missing (therefore NULL) value for creator parameter firstName which is a non-nullable type; nested exception is com.fasterxml.jackson.module.kotlin.MissingKotlinParameterException: Instantiation of [simple type, class com.example.demo.user.User] value failed for JSON property firstName due to missing (therefore NULL) value for creator parameter firstName which is a non-nullable type\n at [Source: (PushbackInputStream); line: 8, column: 1] (through reference chain: com.example.demo.user.User[\"firstName\"])",
  "path": "/api/v1/register"
}

Response code: 400; Time: 214ms; Content length: 119 bytes

Answer 1

Add following property in your spring boot configuration logging.level.org.springframework.web=DEBUG you will get the exact reason for getting 400 Bad requests on console logs.