Java EE UriInfo: append Query parameters

I want to append the query parameters list of a received UriInfo in a Rest service. The query comes from the client with some parameters and I need to add some more in server side.

I tried with:

uriInfo.getQueryParameters().add("Param", "value");

but when I display the URI, it doesn't has the new parameter.

On the other hand, if I do it like this:

URI uri = uriInfo.getRequestUriBuilder().queryParam("Param", "value").build();

when I display the URI, it contains the new parameter. The problem in this second case is to reconstruct a UriInfo object to give to the next functions, they require it.

I've seen that it cannot be instantiated, it has no constructors, it has to be added with @Context, its value can be updated by another UriInfo... but how to create this UriInfo with the URI I modified?