Encoding URL query parameters in Java

How does one encode query parameters to go on a url in Java? I know, this seems like an obvious and already asked question.

There are two subtleties I'm not sure of:

1. Should spaces be encoded on the url as "+" or as "%20"? In chrome if I type in "http://google.com/foo=?bar me" chrome changes it to be encoded with %20
2. Is it necessary/correct to encode colons ":" as %3B? Chrome doesn't.

Notes:

• java.net.URLEncoder.encode doesn't seem to work, it seems to be for encoding data to be form submitted. For example, it encodes space as + instead of %20, and encodes colon which isn't necessary.
• java.net.URI doesn't encode query parameters

Solution 1:

java.net.URLEncoder.encode(String s, String encoding) can help too. It follows the HTML form encoding application/x-www-form-urlencoded.

URLEncoder.encode(query, "UTF-8");

On the other hand, Percent-encoding (also known as URL encoding) encodes space with %20. Colon is a reserved character, so : will still remain a colon, after encoding.

Solution 2:

EDIT: URIUtil is no longer available in more recent versions, better answer at Java - encode URL or by Mr. Sindi in this thread.

URIUtil of Apache httpclient is really useful, although there are some alternatives

URIUtil.encodeQuery(url);

For example, it encodes space as "+" instead of "%20"

Both are perfectly valid in the right context. Although if you really preferred you could issue a string replace.