jsp get方法乱码有关问题

<form action="encoding.jsp" method="post" name="get" >
<input type="hidden" name="luanma1" value="<%//out.print(URLEncoder.encode("中国","ISO-8859-1"));%>"/>
<input type="hidden" name="luanma" value="中国"/>
<input type="submit" name="tijioa" value="tijiao" />
<%
?

String luanma=request.getParameter("luanma");

if(null !=luanma){
?out.println("没有解码："+luanma);
?
?String ns=new String(luanma.getBytes("ISO-8859-1"),"GBK");?
?out.println("解码："+ns);
?System.out.println(ns);

}

%>