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javaurlencode

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

  • 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.