Servlet: doGet not returning - servlets

Question

I receive an image in doPost method from a client application. I'm not supposed to store this image in any folder path, so i use the following code to store this image in session attribute as data byte.
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
String fileName = null;
fileName = request.getParameter("filename");
System.out.println("filename: " + fileName);
DataInputStream din = new DataInputStream(request.getInputStream());
byte[] data = new byte[0];
byte[] buffer = new byte[512];
int bytesRead;
while ((bytesRead = din.read(buffer)) > 0) {
// construct an array large enough to hold the data we currently have
byte[] newData = new byte[data.length + bytesRead];
// copy data that was previously read into newData
System.arraycopy(data, 0, newData, 0, data.length);
// append new data from buffer into newData
System.arraycopy(buffer, 0, newData, data.length, bytesRead);
// set data equal to newData in prep for next block of data
data = newData;
}
request.getSession().setAttribute("imageData", data);
}
I want to retrieve this from doGet method after its received. So, i am trying with the following doGet code to retrieve it.
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
byte[] data = (byte[]) request.getSession().getAttribute("imageData");
int len = data.length;
byte[] imageData = new byte[len];
for(int i=0; i < len; i++) {
imageData[i] = data[i];
}
response.setContentType("image/jpg");
response.getOutputStream().write(imageData);
response.getOutputStream().flush();
response.getOutputStream().close();
}
But, its NOT returning this image in doGet, when i call this servlet from an another client after some time.
Could someone please advise me, what I'm doing wrong here for not getting image in doGet?

Answer 1

I'm not supposed to store this image in any folder path, so i use the following code to store this image in session attribute as data byte.
...
But, its NOT returning this image in doGet, when i call this servlet from an other client after some time.
Session attributes are associated with exactly one client, so one client can not get the session attributes from an other client
You could store the image in the servlet context, like:
ServletContext context = request.getSession().getServletContext();
context.setAttribute("imageData", data);
Later, you can read the attribute from the servlet context.
Or, another possibility is to store the image in a static variable.
However, the image will be stored, although it is in memory. Maybe some Servlet Containers also store Servlet Context attributes on the hard disk.