Servlet乱码

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/plain;charset=UTF-8");
        request.setCharacterEncoding("UTF-8");
        response.setCharacterEncoding("UTF-8");
        String d30502 = request.getParameter("d30502");//姓名
        String d30534 = request.getParameter("d30534");//新证号
        String institution = request.getParameter("institution");
        String date_start = request.getParameter("date_start");
        String date_end = request.getParameter("date_end");
    }