@Size annotation to validate a field

Question

I need to validate a field - secPhoneNumber (secondary phone #). I need to satisfy below conditions using JSR validation

• The field can be empty/null
• Otherwise, the data must be of length 10.

I tried the code below. The field is always getting validated on form submission. How do I validate the field to be of length 10 only when it is not empty?

Spring Form:

<form:label path="secPhoneNumber">
Secondary phone number <form:errors path="secPhoneNumber" cssClass="error" />
</form:label>
<form:input path="secPhoneNumber" />

Bean

@Size(max=10,min=10)
    private String secPhoneNumber;

Answer 1

I think for readability and to use in future times i would create my custom validation class, you only should follow this steps:

1. Add your new custom annotation to your field

   @notEmptyMinSize(size=10)
   private String secPhoneNumber;
   

2. Create the custom validation classes

   @Documented
   @Constraint(validatedBy = notEmptyMinSize.class)
   @Target( { ElementType.METHOD, ElementType.FIELD })
   @Retention(RetentionPolicy.RUNTIME)
   public @interface notEmptyMinSize {
   
   
       int size() default 10;
   
       Class<?>[] groups() default {};
   
       Class<? extends Payload>[] payload() default {};
   
   }
   

3. Add your business logic to your validation

   public class NotEmptyConstraintValidator implements      ConstraintValidator<notEmptyMinSize, String> {
   
        private NotEmptyMinSize notEmptyMinSize;
   
        @Override
        public void initialize(notEmptyMinSize notEmptyMinSize) { 
            this.notEmptyMinSize = notEmptyMinSize
        }
   
        @Override
        public boolean isValid(String notEmptyField, ConstraintValidatorContext cxt) {
           if(notEmptyField == null) {
                return true;
           }
           return notEmptyField.length() == notEmptyMinSize.size();
       }
   
   }
   

And now you could use this validation in several fields with different sizes.

Here another example you can follow example