Question

我在DB中拥有超过100万个数据。我需要一次从DB 1000行读取并将其写入OutputStream，直到没有数据返回为止。我不确定可以有多少数据。因此，直到到达数据末尾，我才知道文件的长度。

是否有可能将数据批量写入输出流，并应同时将其传输到网络。我试图在这里实现的是避免内存不足。如果我在输出流中保留一百万个数据，它将变为OOM。因此，为避免OOM，我尝试将数据写入网络，并且不应将其保存在任何JVM内存中，因此一旦获得它就应将其写入网络。到目前为止，我编写的代码都在这里。

注意：这是独立代码。

    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {
    // TODO Auto-generated method stub
    String header = "Doc Timestamp,Internal DocID,DocType,Sender,Receiver,Routing Status,User Status,External DocID\n";
    resp.setHeader("Content-Disposition", "attachment; filename="+"File.csv"); 
    resp.setContentType("text/csv");

    OutputStream stream = resp.getOutputStream();
    stream.write(header.getBytes());
    stream.flush();

    for (int i = 0; i < 10000000; i++) {
        String docTimeStamp = new Date().toString();
        String docid = UUID.randomUUID().toString();
        String docType = "ICSCSRin";
        String sender = "ACC15796_CWS";
        String receiver = "ACC15794_CWS";
        String routingStatus = "DONE W/ ERRORS";
        String userStatus = "CWS POST_PROCESS";
        String snrf = "CWS_TES";
        StringBuffer str = new StringBuffer();
        str.append(docTimeStamp).append(",").append(docid).append(",").append(docType).append(",").append(sender).append(",").append(receiver).append(",").append(routingStatus).append(",").append(userStatus).append(",").append(snrf).append("\n");
        stream.write(str.toString().getBytes());
    }
    stream.close();
}

动态将csv文件写入servlet响应OutputStream

0 个答案: