Download.java

package finalProj;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


@WebServlet("/Drive/Download")
public class Download extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    @Override
    
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		String name = request.getParameter("fileName");
		 String username=null;
	        Cookie[] cookies = request.getCookies();
			if(cookies != null) {
				for(Cookie cookie : cookies) {
					if(cookie.getName().equals("userName")) {
						username= cookie.getValue();
					}
				}
			}   	
    	
    	// reads input file from an absolute path
        String filePath = getServletContext().getRealPath("/WEB-INF/uploads/" + username +"/"+name);
        File downloadFile = new File(filePath);
        FileInputStream inStream = new FileInputStream(downloadFile);
         
        // gets MIME type of the file
        String mimeType = getServletContext().getMimeType(filePath);
        if (mimeType == null) {        
            // set to binary type if MIME mapping not found
            mimeType = "application/octet-stream";
        }
         
        // modifies response
        response.setContentType(mimeType);
        response.setContentLength((int) downloadFile.length());
         
        // forces download
        String headerKey = "Content-Disposition";
        String headerValue = String.format("attachment; filename=\"%s\"", downloadFile.getName());
        response.setHeader(headerKey, headerValue);
         
        // obtains response's output stream
        OutputStream outStream = response.getOutputStream();
         
        byte[] buffer = new byte[4096];
        int bytesRead = -1;
         
        while ((bytesRead = inStream.read(buffer)) != -1) {
            outStream.write(buffer, 0, bytesRead);
        }
         
        inStream.close();
        outStream.close();   

	}

	@Override
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub

	}

}