Do colons require encoding in URI query parameters?

Question

I've noticed that Java's UriBuilder isn't encoding the : characters included in my query parameter values (ISO 8601-formatted strings).

According to Wikipedia, it seems colon should be encoded.

In particular, encoding the query string uses the following rules:

• Letters (A-Z and a-z), numbers (0-9) and the characters '.','-','~' and '_' are left as-is
• SPACE is encoded as '+' or %20[citation needed]
• All other characters are encoded as %FF hex representation with any non-ASCII characters first encoded as UTF-8 (or other specified encoding)

So, what's the deal? Should colons in query parameters be encoded or not?

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Update:

I looked up the URI Syntax spec (RFC 3986) and it looks like encoding colons in query params really isn't necessary. Here's an excerpt from the ABNF for URI:

URI         = scheme ":" hier-part [ "?" query ] [ "#" fragment ]
query       = *( pchar / "/" / "?" )
pchar         = unreserved / pct-encoded / sub-delims / ":" / "@"
unreserved    = ALPHA / DIGIT / "-" / "." / "_" / "~"
pct-encoded   = "%" HEXDIG HEXDIG
sub-delims    = "!" / "$" / "&" / "'" / "(" / ")" / "*" / "+" / "," / ";" / "=

Answer 1

Yes, they should be encoded in a query string. The correct encoding is %3A

However, I can understand why UriBuilder isn't encoding :. You don't want to encode the colon after the protocol (eg http:) or between the username and password (eg ftp://username:[email protected]) in an absolute URI.