UserController.kt

@GetMapping("/users/{id}")
fun specificUser(@PathVariable id: Int): ResponseEntity<EntityModel<User>> {
    if(dataBean.users.filter { it.id == id }.isEmpty()){
        return ResponseEntity(HttpStatus.NOT_FOUND)
    }
    return ResponseEntity(EntityModel(dataBean.users.filter { it.id == id }.first(),
            linkTo(methodOn(UserController::class.java).specificUser(id)).withSelfRel(),
            linkTo(methodOn(UserController::class.java).allUsers()).withRel("users")), HttpStatus.OK)
}