SpringMVC Converter Exception Handling - spring

Question

I implemented a converter to convert String to UUID and include length validation.
public class StringToUUIDConverter implements Converter<String, UUID> {
public UUID convert(String source){
if(source.length>36){
throw new RuntimeException();
}else{
return ...
}
}
}
At first, I thought I would get a RuntimeException when I passed in a string of length 37. However, I tested it and found that no exception was thrown.
Code snippet of TypeConverterDelegate.convertIfNecessary()
if (editor == null && conversionService != null && newValue != null && typeDescriptor != null) {
TypeDescriptor sourceTypeDesc = TypeDescriptor.forObject(newValue);
if (conversionService.canConvert(sourceTypeDesc, typeDescriptor)) {
try {
return (T) conversionService.convert(newValue, sourceTypeDesc, typeDescriptor);
}
catch (ConversionFailedException ex) {
// fallback to default conversion logic below
conversionAttemptEx = ex;
}
}
}
ConversionUtils convert all exception to ConversionFailedException :
abstract class ConversionUtils {
#Nullable
public static Object invokeConverter(GenericConverter converter, #Nullable Object source,
TypeDescriptor sourceType, TypeDescriptor targetType) {
try {
return converter.convert(source, sourceType, targetType);
}
catch (ConversionFailedException ex) {
throw ex;
}
catch (Throwable ex) {
throw new ConversionFailedException(sourceType, targetType, source, ex);
}
}
}
TypeConverterDelegate catches the exception I throw and follows another set of logic to convert String to UUID. Although I've done what I want with InitBinder, what should I do if I really want to throw an exception here?