servlet to display a pdf file using by overriding doPost()

Question

i want to web app that takes in a pdf file and displays it but i got a http 500 error.i thought it was get extracting the byte array from the request and adding it to the response output stream. well where was i wrong?

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
    response.getOutputStream().write(request.getParameter("f").getBytes());
    response.getOutputStream().flush();
    response.getOutputStream().close();
}

here is the html page

<body>
<form action="display" method="post" enctype="multipart/form-data">
PDF FILE : <input type="file" name="f">
<input type="submit" value="display">
</form>
</body>

here is the error that i got

java.lang.NullPointerException
    display.doPost(display.java:43)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:722

Use Apache commons-fileupload for it. – Sergey Morozov Sep 25 '13 at 09:20 — Sergey Morozov, Sep 25 '13 at 09:20

score 2 · Answer 1 · answered Sep 25 '13 at 09:19

You should get a valid part from your multipart request. You can use Apache Commons FileUpload, or with Servlets 3.0 Spec:

Part filePart = request.getPart("f"); // Retrieves <input type="file" name="f">
InputStream filecontent = filePart.getInputStream();
// ... read input stream

score 0 · Answer 2 · edited Sep 25 '13 at 09:40

0

You want to send an PDF file to the browser, you should write a response.setContentType("application/pdf") before outputStream writes the stream;

edited Sep 25 '13 at 09:40

Alexis Pigeon

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answered Sep 25 '13 at 09:24

user2814530

1

yeah but i got a null pointer exception...do you think that would have happened because i dint set the content type? – Alvin Sep 25 '13 at 09:35

user2795605 · Answer 3 · 2013-09-25T09:42:06.913

Make sure to call response.getOutputStream() only once:

OutputStream os = response.getOutputStream();
os.write(bytes);
os.flush();
os.close();

The uploaded file is not contained as a request parameter. That is the reason for the NullPointerException in your code. You must get the pdf content via the request's input stream. Use a third pary library or Servlet 3 spec for that purpose.

If you like to set http headers (i.e. for the content type), you should set them before writing any bytes to the OutputStream via response.setHeader().

servlet to display a pdf file using by overriding doPost()

3 Answers3