How to determine if a String contains invalid encoded characters

Question

Usage scenario

We have implemented a webservice that our web frontend developers use (via a php api) internally to display product data. On the webs

Answer 1

URLDecoder will decode to a given encoding. This should flag errors appropriately. However the documentation states:

There are two possible ways in which this decoder could deal with illegal strings. It could either leave illegal characters alone or it could throw an IllegalArgumentException. Which approach the decoder takes is left to the implementation.

So you should probably try it. Note also (from the decode() method documentation):

The World Wide Web Consortium Recommendation states that UTF-8 should be used. Not doing so may introduce incompatibilites

so there's something else to think about!

EDIT: Apache Commons URLDecode claims to throw appropriate exceptions for bad encodings.