RepositoryRestConfiguration.java

@Autowired(required = false)
RestConversionService customConversionService = new RestConversionService();

/**
* Either the user's pre-configured {@link ConversionService} or the
* {@link DefaultConversionService}.
* 
* @return
*/
@Bean
ConversionService conversionService() {
	if (null != customConversionService) {
		return customConversionService;
	} else {
		defaultConversionService.addConverter(new StringToUUIDConverter());
		return defaultConversionService;
	}
}

RestConversionService.java

public class RestConversionService extends DefaultConversionService
{
	
	public RestConversionService() {
		addConverter(new StringToUUIDConverter());
	}
}

StringToUUIDConverter.java

public class StringToUUIDConverter implements Converter<String, UUID> {

	public UUID convert(String source) {
		if (source != null)
			return UUID.fromString(source);
		else
			return null;
	}
}