question: public List < ValidationErrorMessage > validateValue ( String value ) { errorMessageIds . clear ( ) ; if ( dataRestrictions . isRequired ( ) && valueNullOrEmpty ( value ) ) { errorMessageIds . add ( new ValidationErrorMessage ( "required" , id , null ) ) ; } else { if ( ! valueNullOrEmpty ( value ) ) { for ( AbstractValidationRule rule : dataRestrictions . getValidationRules ( ) ) { if ( ! rule . validate ( value ) ) { errorMessageIds . add ( new ValidationErrorMessage ( rule . getMessageId ( ) , id , rule ) ) ; } } } } return errorMessageIds ; }
target:  Gets all errormessagecodes for this field's value. This list is filled after doing isValid() on this field