Java调用存储过程

Connection conn = null;
        ResultSet rs = null;
        CallableStatement statm = null;
        List listVo = new ArrayList();
        //调用存储过程，返回sql
            conn = JdbcUtil.getConnection();
            statm = conn.prepareCall("{call pro_rpt_all_statistics_s(?,?,?)}");
            statm.registerOutParameter(3, java.sql.Types.VARCHAR);
            statm.setString(1, month);
            statm.setString(2, dept);
            statm.executeUpdate();
            String result = statm.getString(3);
            PreparedStatement ps = conn.prepareStatement(result);
            rs = ps.executeQuery();