spring-projects/spring-hateoas

@gregturn @odrotbohm Thanks for the response, I try to explain again where I have a conceptional ("knopf-im-kopf") problem in my head. I try to follow (resp. impl) https://speakerdeck.com/olivergierke/domain-driven-design-and-rest-1?slide=15

Also use this classes to validate on the API side. When I have to use this classes then also to create my _links I have to pass also valid (from my business valid objects) values (what is normal because of validation)

If I use the same (what 1st come in my head who should be correct) objects.

I was asking my self don't if it better to don't use the same object on API side. because the java.lang.IllegalArgumentException are throwing on runtime and If the developer not have the Domain validation in mine when he create the HATEOS resp. _links with the methodOn(...

@gregturn when I get U right is it also valid to create the API validation from the service layer (after transformation)

data class Customer(val id: String? = UUID.randomUUID().toString(), val firstName: FirstName, val lastName: LastName)
// Domain Primitive
data class FirstName(val value: String) {
    init {
        require(value.isNotEmpty()) { "value must be non-empty" }
        require(value.trim().length >= 2) { "wrong value length" }
        require(value.trim().length <= 20) { "wrong value length" }
    }
    companion object {
        @JvmStatic
        @JsonCreator
        fun create(value: String) = FirstName(value)
    }
    @JsonValue
    override fun toString() = value
}
.....

@RestController
class CustomerResource(private val service: CustomerService) {
    val CREATE_REL = "create"
    val ALL_CUSTOMERS_REL = "customers"

    @GetMapping(value = ["/customers/{id}"], produces = [MediaTypes.HAL_JSON_VALUE])
    fun oneCustomer(@PathVariable id: String): EntityModel<Customer> {
        val customer = Customer(
            id = null, firstName = FirstName("Here-I-Have-To-Add-Some-Valid-Domain-Primitive-Value"),
            lastName = LastName("TO-Avoid-IllegalArgumentException")
        )
        // java.lang.IllegalArgumentException: wrong value length
        //    at ch.keepcalm.demo.customer.secureByDesignModel.FirstName.<init>(Customer.kt:13)

        val selfLink = linkTo(methodOn(CustomerResource::class.java).oneCustomer(id)).withSelfRel()
        val createCustomerLink = linkTo(methodOn(CustomerResource::class.java).addCustomer(customer = customer)).withRel(CREATE_REL)
        val allCustomersLink = linkTo(methodOn(CustomerResource::class.java).allCustomers()).withRel(ALL_CUSTOMERS_REL)

        return EntityModel.of(service.findCustomerById(id))
            .add(selfLink, createCustomerLink, allCustomersLink)
    }

    @GetMapping(value = ["/customers"], produces = [MediaTypes.HAL_JSON_VALUE])
    fun allCustomers(): CollectionModel<EntityModel<Customer>> {
        val selfLink: Link = linkTo(methodOn(CustomerResource::class.java).allCustomers()).withSelfRel()
        return CollectionModel.of(
            service.findCustomers().map {
                EntityModel.of(it, linkTo(methodOn(CustomerResource::class.java).oneCustomer(it.id.toString())).withSelfRel())
            }, selfLink
        )
    }
}