Post Validation didn't work with Spring-Boot Swagger RestAPI - spring-boot

Question

I'm currently working on a Cross Platform App to record the expenses and the incomes. So far so good. However, when I want to add a Backend Post Validation (so nobody can save incomes like €19,99999 etc.) the Post Validation does not work. It would be great if somebody could help me. Here are the details:
I am adding the springfox-bean-validation to my Backend
Entity
#ApiModel(
value = "Expense",
description =
"Information of all expenses with cost, expense date as well as the purpose to which these expenses went"
)
#Entity
#Table(name = "Expenses")
data class Expense(
#ApiModelProperty(notes = "Cost of the Expense in €")
#DecimalMin(value = "0.0", inclusive = false, message = "Price have to be higher than 0.0")
#Digits(integer = Int.MAX_VALUE, fraction = 2, message = "Price have only 2 decimal places")
var cost: BigDecimal,
#ApiModelProperty(notes = "Creation date of the Expense")
#NotNull(message = "Date may not be Null")
var date: LocalDate,
#ApiModelProperty(notes = "Purpose of the expense")
var purpose: String?
) : DbEntity() {
constructor() : this(BigDecimal.ZERO, LocalDate.now(), "")
}
Controller
#CrossOrigin
#RestController
#Api(value = "/finance", description = "FinanceController", produces = "application/json")
#RequestMapping("/api/finance")
class FinanceController(
private val expenseRepository: ExpenseRepository
) {
#ApiOperation(value = "Create an Expense", response = Expense::class)
#PostMapping("/expanse")
fun createExpense(#RequestBody expenseInfo: Expense): Expense {
return expenseRepository.save(expenseInfo)
}
}
SpringFoxConfig
#Configuration
#EnableSwagger2
#Import(BeanValidatorPluginsConfiguration::class)
class SwaggerConfiguration {
#Bean
fun api(): Docket = Docket(DocumentationType.SWAGGER_2)
.select()
.apis(RequestHandlerSelectors.any())
.paths(PathSelectors.any())
.build()
}
And that is the resulting Output from the swagger UI. Why are there no annotations like #NotNull or #Digits(...)?
When I test a Post request, I get 200 as HTTP Response Code and no Error!
{
"cost": 19.99999999,
"date": "2020-06-06",
"purpose": "test",
"id": 15
}