How to encode and shorten hash for url safety?

Question

I use SHA-512 to hash a token, which results in a 128 character string. How can I encode it so that it is shorter but still URL safe (no need to escape like '+' or '&')?

Hex and Base32 are both suboptimal, and Base64 is unsafe. I don't want to hack up a custom Base62 codec, as that will only become a maintenance burden.

Answer 1

Java 8 added Base64 encoders, with different flavors. See java.util.Base64

For example:

Base64.getUrlEncoder().encode(...);

Answer 2

Google has you covered:

com.google.common.io.BaseEncoding#base64Url

This is an efficient Base64 codec that only uses url-safe characters. It will produce a String with a length of 88 characters for a SHA512 hash.