How to apply hibernate validation to Character type?

@Pattern(regexp = "^[M|F]{1}$", message ="Must be M or F")
private Character gender;

Result:

javax.validation.UnexpectedTypeException: HV000030: No validator could be found for type: java.lang.Character.

How can achieve the following:

apply hibernate validation to the character using a regex pattern
restricting the return type to be a single letter (that's why I chose char)
to everything of this in a single method?

Solution

I had similiar problem and i didnt find any default hibernate validator annotation for that. But there is easy way to create custom annotation. (look here https://docs.jboss.org/hibernate/validator/5.1/reference/en-US/html/validator-customconstraints.html) Below example with sex:

@Target({ METHOD, FIELD, ANNOTATION_TYPE })
@Retention(RUNTIME)
@Constraint(validatedBy = SexValidator.class)
@Documented
public @interface Sex
{

    String message() default "{customValidator.sex";

    Class<?>[] groups() default {};

    Class<? extends Payload>[] payload() default {};

    @Target({ FIELD, METHOD, ANNOTATION_TYPE })
    @Retention(RUNTIME)
    @Documented
    @interface List
    {
        Sex[] value();
    }
}

public class SexValidator implements ConstraintValidator<Sex, Character> {

    public void initialize(Sex sex)
    {
        // used only if your annotation has attributes
    }

    public boolean isValid(Character sex, ConstraintValidatorContext constraintContext)
    {
        // Bean Validation specification recommends to consider null values as
        // being valid. If null is not a valid value for an element, it should
        // be annotated with @NotNull explicitly.
        if (sex == null)
        {
            return true;
        }
        if (sex.equals('F') || sex.equals('M'))
            return true;

        else
        {
            return false;
        }

    }
}

@Column(name = "sex", columnDefinition = "char(1)")
@NotNull
@Sex
private Character sex;