为什么POST不支持charset，而AJAX请求却支持呢?tomcat 6

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() in utf-8. When submitting via form post, the data is returned from getParameter() in iso-8859-1. I have a tomcat based application that needs to