[CODEC-75] Make Base64 URL-safe

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.3
• Fix Version/s: 1.4
• Assignee: Gary D. Gregory
• Reporter: Julius Davies
• Created: 23/May/09 18:52
• Updated: 09/Oct/12 18:17
• Resolved: 13/Jul/09 20:49

Description

Regular Base64 uses + and / for code point 62 and 63. URL-Safe Base64 uses - and _ instead. Also, URL-Safe base64 omits the == padding to help preserve space.

http://en.wikipedia.org/wiki/Base64#URL_applications

Approach:

decode() should be able to seamlessly handle either situation. This means interpreting +- and /_ as equivalents at any time during the decode. decode() also needs to be more robust against missing padding characters.

encode() should either emit +/ or -_ depending on a mode set during Base64 construction.

Since URL-SAFE is all about URL's (e.g. HTTP GET) and most browsers are limited to 1KB of query string, I do not think we need to bother making the URL-MODE available in the stream-oriented classes. (Nonetheless, the streams should be able to decode URL-SAFE, but I don't think they should produce it).

—

Some background information: I'm putting together a webapp that integrates with MS Active Directory. Users and Groups are keyed of objectGUID with is a 128 bit int. Would be nice to get some support for this kind of thing:

"Click to view the profile of <a href='?u=_3-PwBzbRxqMi1qTBhg_6A'>Julius Davies</a>."

Right now I'm using Hex:

"Click to view the profile of <a href='?u=ff7f8fc01cdb471a8c8b5a9306183fe8'>Julius Davies</a>."

Current Base64 class would output this, and I suspect the + would screw things up:

"Click to view the profile of <a href='?u=/3+PwBzbRxqMi1qTBhg/6A=='>Julius Davies</a>."

Issue Links

• incorporates: WICKET-2171 Base64UrlSafe claims to be RFC 3548 compliant, but isn't
• is duplicated by: CODEC-36 [codec] Support of Base 64 Encoding with URL and Filename Safe Alphabet
• relates to: CODEC-160 Base64.encodeBase64URLSafeString doesn't add padding characters at the end.