While great, Jsoup is a HTML parser, not a JSON parser, so it is useless in this context. If you ever attempt it, Jsoup will put the returned JSON implicitly in a <html><head> and so on. You don't want to have that. Gson is a JSON parser, so you definitely need it.
Your concrete problem is likely that you don't know how to feed an URL returning a JSON to Gson. In that case, you need to use URL#openStream() to get an InputStream of it and use InputStreamReader to decorate it into a Reader which finally can be fed to Gson#fromJson() which accepts a Reader.
InputStream input = new URL("http://example.com/foo.json").openStream();
Reader reader = new InputStreamReader(input, "UTF-8");
Data data = new Gson().fromJson(reader, Data.class);
// ...
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