HV000030: No validator could be found for constraint 'javax.validation.constraints.Size' validating type 'java.util.Optional<java.lang.String>'

Question

Hello guys I'm trying to get the validation on the YAML

- name: campo
        in: query
        schema:
          type: string
          pattern: '[S|N]' #pattern
          maxLength: 1

Using maven spring boot and delegate. On the RestController I added annotation @Validated and I'm able to validate required=true fields, but if fields are not require, as per architecture design, parameter will be Optional<String>. For this java.util.Optional, trying to test and validate, throw title error:

{
  "timestamp": "2020-10-21T07:50:18.651+0000",
  "status": 500,
  "error": "Internal Server Error",
  "message": "HV000030: No validator could be found for constraint 'javax.validation.constraints.Size' validating type 'java.util.Optional<java.lang.String>'. Check configuration for 'metodo.campo'",
  "path": "/%7BbasePath%7D/microservicio/metodo"
}

¿Anyway to solve this issue to have this Optional<String> validation proccessed correctly? We don't want to write all code for validation on Java if can be done on YAML + validation (@Valid and @Validated).

EDIT: The validation @Size and others is generated from YAML with open api version 3.0.3

Answer 1

You should write: Optional<@Size String> (which would check the size of the String inside the optional) instead of @Size Optional<String> (which is supposed to check the size of the optional, which is meaningless).

See Hibernate Validator: With java.util.Optional:

package org.hibernate.validator.referenceguide.chapter02.containerelement.optional;

public class Car {

    private Optional<@MinTowingCapacity(1000) Integer> towingCapacity = Optional.empty();

    //...

}