<p>I need to pass a UUID instance via http request parameter. Spring needs a custom type converter (from String) to be registered. How do I register one?</p>

Not sure what you are asking?
Spring comes with a
CustomEditorConfigurer
to supply custom String <-> Object converters.
To use this, just add the CustomEditorConfigurer as bean to your config, and add the custom converters. However, these converters are typically used when converting string attributes in the config file into real objects.
If you are using Spring MVC, then take a look at the section on
annotated MVC
Specifically, have a look at the
@RequestParam
and the
@ModelAttribute
annotations?
Hope this helps?