getWriter() has already been called

Question

public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        out.print( " <script> alert( 'Booking successfully ') </script> ");
        ByteArrayOutputStream out1 = QRCode.from(all).to(ImageType.PNG).stream();
            response.setContentType("image/png");
            response.setContentLength(out1.size());
            
           OutputStream outStream = response.getOutputStream();
            outStream.write(out1.toByteArray());            outStream.flush();                        
            outStream.close();上網看過,只能用其中一個.但是我想用2個. 怎樣做. 另外,我試過加out.clear() 和out = pageContext.pushBody(); 就出錯.cannot find symbol.

Answer 1

你是想显示图片吧。直接<img src="ImgServlet" />获取图片。也就是图片另外用个servlet。

Answer 2

你那段script代码完全可以拿到jsp里控制，而且你的这种逻辑有必要吗

Answer 3

我只是選了少部分的代碼出來..image我是把value轉為QR code.所以會用到outputstream

Answer 4

原本的代碼    @Override
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();        String doc_id = request.getParameter("doctor").toString();
        String TIME1 = request.getParameter("time");
        String date1 = request.getParameter("datepicker");
        SimpleDateFormat sdf = new SimpleDateFormat("yy-MM-dd");
        SimpleDateFormat sdf1 = new SimpleDateFormat("HH:mm");
        HttpSession session = request.getSession(true);
        //connect database
        PreparedStatement statement = null;
        Statement stmt = null;
        ResultSet rs = null;
        try {
            Class.forName(driver).newInstance();
            con = DriverManager.getConnection(url + dbName, username, password);
            stmt = con.createStatement();            statement = con.prepareStatement("INSERT INTO booking (booking_id,client_id,doctor_id,booking_date,booking_time,status) VALUES(?,?,?,?,?,?)");
            rs = stmt.executeQuery("select count(*)+1 as rowCount from booking");
            java.util.Date date = new java.util.Date();
            java.util.Date time1 = new java.util.Date();
            date = sdf.parse(date1);
            time1 = sdf1.parse(TIME1);
                       rs.next();
            int count = rs.getInt("rowCount");
            if (count < 10) {
                statement.setString(1, "B0000" + count);
            } else if (count >= 10 || count <= 99) {
                statement.setString(1, "B000" + count);
            }else if(count>=100 || count<=999){
                statement.setString(1, "B00" + count);
            }
            statement.setString(2, (String) session.getAttribute("Username"));
            statement.setString(3, doc_id);
            statement.setDate(4, new java.sql.Date(date.getTime()));
            statement.setTime(5, new java.sql.Time(time1.getTime()));
            statement.setString(6, "N");
            statement.executeUpdate();
           out.print( " <script> alert( 'Booking successfully ') </script> ");
            
            String qrtext2 = request.getParameter("subject").toString();
            String all="client id: "+session.getAttribute("Username")+"\n"+"doc id: "+doc_id+"\n"+"subject: "+qrtext2+"\n"+"Date: "+date1+"\n"+"Time: "+TIME1;              ByteArrayOutputStream out1 = QRCode.from(all).to(ImageType.PNG).stream();
            response.setContentType("image/png");
            response.setContentLength(out1.size());
            
           OutputStream outStream = response.getOutputStream();
            outStream.write(out1.toByteArray());            outStream.flush();                        
            outStream.close();
            
            //out.clear();
//out = pageContext.pushBody();        } catch (Exception e) {
            out.print(e);
        } finally {
            try {
                statement.close();
                rs.close();
                stmt.close();
                con.close();
                out.close();            } catch (Exception e) {
            }
            out.close();
        }
    }

Answer 5

一样的道理，另外写个servlet,你可以把ID传过去再获取你要的东西

Answer 6

現在我弄清楚了..直接out print<img src=servlet?all
 
servlet: 放入qr code代碼和getParameter("all");但是最後出來的是死圖.

Answer 7

解決了..
加out.print("<img src="+request.getContextPath()+"/QRcode?bid="+all+">"); 就可以了