Why does POST not honor charset, but an AJAX request does? tomcat 6

Question

I have a tomcat based application that needs to submit a form capable of handling utf-8 characters. When submitted via ajax, the data is returned correctly from getParameter

Answer 1

I implemented a filter based on the information in this post and it is now working. However, this still doesn't explain why even though the page was UTF-8, the charset used by tomcat to interpret it was ISO-9951-1.