Converter from @PathVariable DomainObject to String? (using ControllerLinkBuilder.methodOn)

Question

I'm trying to call Spring's ControllerLinkBuilder.methodOn() with a non-String type, which always fails. And I don't know which kind of Converter to use and where to register it.

Here's my Controller:

@RestController
@RequestMapping("/companies")
class CompanyController {

    @RequestMapping(value="/{c}", method=RequestMethod.GET)
    void getIt(@PathVariable Company c) {
        System.out.println(c);
        Link link = linkTo(methodOn(getClass()).getIt(c));
    }

}

The System.out.println(c) works well. My Company Domain object get's fetched from DB. (I'm using DomainClassConverter)

But the other way doesn't work: ConverterNotFoundException: No converter found capable of converting from type @PathVariable Company to type String

Do I just need a Converter<Company, String>? And where should I register it? I tried something within the addFormatters(FormatterRegistry registry) method of WebMvcConfigurationSupport, but it did just display the same error. But after all I'm not sure what exactly I tried...

Answer 1

I had the same issue, it is a bug. If you don't want to do copy & paste on every controller you can try something like this in your WebMvcConfigurationSupport. It works for me.

@Override
public void addFormatters(final FormatterRegistry registry) {
    super.addFormatters(registry);

    try {
        Class<?> clazz = Class.forName("org.springframework.hateoas.mvc.AnnotatedParametersParameterAccessor$BoundMethodParameter");
        Field field = clazz.getDeclaredField("CONVERSION_SERVICE");
        field.setAccessible(true);
        DefaultFormattingConversionService service = (DefaultFormattingConversionService) field.get(null);
        for (Converter<?, ?> converter : beanFactory.getBeansOfType(Converter.class).values()) {
            service.addConverter(converter);
        }
    }
    catch (Exception ex) {
        throw new RuntimeException(ex);
    }
}