package cn.jbit.download.servlet;  import java.io.IOException;  import javax.servlet.RequestDispatcher; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;  public class DownloadServlet extends HttpServlet {    private static final long serialVersionUID = 6765085208899952414L;    public void doGet(HttpServletRequest request, HttpServletResponse response)       throws ServletException, IOException {     doPost(request, response);   }    public void doPost(HttpServletRequest request, HttpServletResponse response)       throws ServletException, IOException {     String filedownload = "/upload/1/10213.jpg";//即將下載的文件的相對路徑     String filedisplay = "10213.jpg";//下載文件時顯示的文件保存名稱     response.setContentType("application/x-download");//設置為下載application/x-download     //response.setContentType("application/x-msdownload");//設置為下載application/x-msdownload     //response.setContentType("application/octet-stream");//設置為下載application/octet-stream     response.addHeader("Content-Disposition", "attachment;filename="         + filedisplay);          try {       RequestDispatcher rd = request.getRequestDispatcher(filedownload);       if(rd != null)       {         rd.forward(request,response);       }       response.flushBuffer();     } catch (Exception e) {       e.printStackTrace();     }   } } 

package cn.jbit.download.servlet;  import java.io.BufferedInputStream; import java.io.BufferedOutputStream; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream;  import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;  public class DownloadOfIOServlet extends HttpServlet {  public void doGet(HttpServletRequest request, HttpServletResponse response)       throws ServletException, IOException {     doPost(request, response);   }      public void doPost(HttpServletRequest request, HttpServletResponse response)       throws ServletException, IOException {     String basePath = request.getSession().getServletContext().getRealPath("/upload");      String filedisplay = "helloworld.jpg";     String filedownload = basePath + File.separator + "helloworld.jpg";     response.setContentType("applicaiton/x-download");     response.addHeader("Content-Disposition", "attachment;filename="+filedisplay);          InputStream is = null;     OutputStream os = null;     BufferedInputStream bis = null;     BufferedOutputStream bos = null;          is = new FileInputStream(new File(filedownload));     bis = new BufferedInputStream(is);     os = response.getOutputStream();     bos = new BufferedOutputStream(os);          byte[] b = new byte[1024];     int len = 0;     while((len = bis.read(b)) != -1){       bos.write(b,0,len);     }          bis.close();     is.close();     bos.close();     os.close();   } }