URL encoding using the new Spring UriComponentsBuilder

I'm attempting to use spring's UriComponentsBuilder to generate some urls for oauth interaction. The query parameters include such entities as callback urls and parameter values with spaces in them.

Attempting to use UriComponentBuilder (because UriUtils is now deprecated)

UriComponentsBuilder urlBuilder = UriComponentsBuilder.fromHttpUrl(oauthURL);
urlBuilder.queryParam("client_id", clientId);
urlBuilder.queryParam("redirect_uri", redirectURI);
urlBuilder.queryParam("scope", "test1 test2");

String url = urlBuilder.build(false).encode().toUriString();

Unfortunately, while the space in the scope parameter is successfully replaced with '+', the redirect_uri parameter is not at all url encoded.

E.g,

redirect_uri=https://oauth2-login-demo.appspot.com/code

should have ended up

redirect_uri=https%3A%2F%2Foauth2-login-demo.appspot.com%2Fcode

but was untouched. Diving into the code, specifically org.springframework.web.util.HierarchicalUriComponents.Type.QUERY_PARAM.isAllowed(c) :

if ('=' == c || '+' == c || '&' == c) {
  return false;
}
else {
  return isPchar(c) || '/' == c || '?' == c;
}

clearly allows ':' and '/' characters, which by gum, it shouldn't. It must be doing some other type of encoding, though for the life of me, I can't imagine what. Am I barking up the wrong tree(s) here?

Thanks

UriComponentsBuilder is encoding your URI in accordance with RFC 3986, with section 3.4 about the 'query' component of a URI being of particular note.

Within the 'query' component, the characters '/' and ':' are permitted, and do not need escaping.

To take the '/' character for example: the 'query' component (which is clearly delimited by unescaped '?' and (optionally) '#' characters), is not hierarchical and the '/' character has no special meaning. So it doesn't need encoding.

from what I understand, UriComponentsBuilder doesn't encode the query parameters automatically, just the original HttpUrl it's instantiated with. In other words, you still have to explicitly encode:

String redirectURI= "https://oauth2-login-demo.appspot.com/code";
urlBuilder.queryParam("redirect_uri", URLEncoder.encode(redirectURI,"UTF-8" ));