String username2 = request.getParameter("username");//通过key获取值
Enumeration enu=request.getParameterNames();
HashMap<String,String> map = new HashMap();
while(enu.hasMoreElements()) {
String paraName=(String)enu.nextElement();
map.put(paraName,request.getParameter(paraName));//获取所有key与value,添加到map集合
}