Implement a Simple File Download Servlet
To implement a simple file download servlet, follow these steps:
-
Create a Servlet:
- In web.xml, register a servlet with the URL pattern /download.
-
Implement the Servlet:
- In the doGet() method, retrieve the file ID from the request.
- Query the database for the file name and type using the file ID.
- Set the Content-Type header to specify the file type (e.g., application/pdf).
- Set the Content-disposition header to instruct the browser to download the file (e.g., attachment; filename=yourcustomfilename.pdf).
- Retrieve the file from the file system based on the file name.
- Send the file contents to the response output stream in chunks.
Here's an example servlet implementation:
public class DownloadServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String id = request.getParameter("id");
// Retrieve file name and type using ID from database
response.setContentType("fileType");
response.setHeader("Content-disposition", "attachment; filename=yourcustomfilename.pdf");
File file = new File("fileName");
OutputStream out = response.getOutputStream();
try (FileInputStream in = new FileInputStream(file)) {
byte[] buffer = new byte[4096];
int length;
while ((length = in.read(buffer)) > 0) {
out.write(buffer, 0, length);
}
} finally {
out.flush();
}
}
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