Question

getting an IOExcepiton on the PrintWriter when doing this in doPost method of servlet class:

doPost(HttpServletRequest request,
        HttpServletResponse response){
    String replyMessage = "STATUS_ACCEPT";
    response.setStatus(HttpServletResponse.SC_OK);
    response.setContentType("text/plain; charset=utf-8");

    response.setContentLength(replyMessage.length());
    response.setIntHeader("content-length", replyMessage.length());
    response.getWriter().println(replyMessage);//getting IOException closed on calling this method
    response.flushBuffer();}

If I use the outputstream for sending data there is no error:

    ServletOutputStream outputStream = response.getOutputStream();
    byte[] result = "STATUS_ACCEPT".getBytes("UTF-8");

    response.setStatus(HttpServletResponse.SC_OK);
    response.setContentType("text/plain; charset=utf-8");

    response.setContentLength(result.length);
    response.setIntHeader("content-length", result.length);

    outputStream.write(httpOutData);

how should i use the printwriter for not getting the IOException?

Answer 1

Most like the reason is this:

response.setContentLength(replyMessage.length());
// ...
response.getWriter().println(replyMessage)

Which means, that your response content is at least one byte longer than announced by setContentLenght: The trailing newline appended by println(). Perhaps the difference is two bytes: CR and LF.

Note: If you fix this you will still have problems in the general case: You set the content length to the number of characters which in UTF-8 encoding is not always the number of bytes. setContentLength() wants the number of bytes.

Therefore it would be better to simply delete all code fiddling with the content-length because if you don’t set it, it will be calculated automatically.