custom converters not registered in spring boot

Question

I'm new to Spring Boot. In my Controller I'm using UUIDs as @PathVariable. By default spring returns MethodArgumentTypeMismatchException when passing an invalid UUID.

When the client passes an invalid UUID I want to throw a custom InvalidUUIDException, so that I'm able to return a customized ErrorDto using this Exception.

To archieve that I'm trying to register a custom UUIDConverter (implementing org.springframework.core.convert.converter.Converter).

@Component
public class UUIDConverter implements Converter<String, UUID>
{
    private static final Pattern pattern = Pattern.compile("[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}");

    @Override
    public UUID convert(String input) throws InvalidUuidException
    {
        if (!pattern.matcher(input).matches()) {
            throw new InvalidUuidException(input);
        }

        return UUID.fromString(input);
    }
}

To register this component, I'm adding this Converter to springs ConversionService. Using the ConversionServiceFactoryBean.

@Configuration
public class ConversionServiceConfiguration
{
    @Bean
    public ConversionServiceFactoryBean conversionService()
    {
        ConversionServiceFactoryBean bean = new ConversionServiceFactoryBean();
        bean.setConverters(getConverters());

        return bean;
    }

    private Set<Converter> getConverters()
    {
        Set<Converter> converters = new HashSet<>();
        converters.add(new UUIDConverter());

        return converters;
    }
}

I've tried also to use @Component instead of @Configuration as it was mentioned here: Spring not using mongo custom converters

Other solutions I tried out: Naming the bean conversionServiceFactoryBean instead of conversionService. Or calling bean.afterPropertiesSet() and retuning a ConversionService using bean.getObject() ...

I've also tried to extend from WebMvcConfigurerAdapter, overriding addFormatters and add my converter there using addConverter...

As mentioned here: How to register custom converters in spring boot? I've also tried to register the converter as a @Bean directly.

It does not matter what I tried out, the UUIDConverter will not be applied.

What is the correct solution do something like that in spring-boot?
Can anyone help here? What I'm doing wrong?

Answer 1

I only know about this issue because I've done the same myself with another class and spent hours debugging...

The UUIDConverter is a bean already a registered by Spring itself. Choose literally any other name and you should see it appear.