jsp弹窗并跳转

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        response.setCharacterEncoding("GBK");

        String name = request.getParameter("textfield1");

        String pwd = request.getParameter("textfield2");

        String head = "<meta http-equiv=\"Content-Type\" content=\"text/html; charset=utf-8\" />";

        Sql sql = new Sql();

        PrintWriter out = response.getWriter();

        Connection conn = DbUtil.getConnection();

        try {

            PreparedStatement ps = conn.prepareStatement(sql.getInsert());

            PreparedStatement ps2 = conn.prepareStatement(sql.getSelect());

            ps.setObject(1,name);

            ps.setObject(2,pwd);

            ps2.setObject(1,name);

            ResultSet rs = ps2.executeQuery();

            if (rs.next()){

                response.getWriter().write("<script > alert(\"用户已经存在！请重新输入用户名！\");location='register.jsp';</script>");

            }else{

                ps.execute();

            }

        } catch (SQLException e) {

            e.printStackTrace();

        }

    }

### response.getWriter().write("<script > alert(\"用户已经存在！请重新输入用户名！\");location='register.jsp';</script>");