import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

 
/**
* Servlet implementation class DownloadServlet
*/
public class DownloadServlet extends HttpServlet {

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//獲取需要下載文件名稱
String filename = request.getParameter("filename");
//獲取下載的類型
response.setContentType(this
 
.getServletContext().getMimeType(filename));
//告知客戶端需要下載
response.setHeader("Content-Disposition", "attachment;filename="+filename);
//獲取文件的絕對路徑
String path = this.getServletContext().getRealPath("download/"+filename);
//獲取文件的輸入源
InputStream in = new FileInputStream(path);
//獲取輸出流
ServletOutputStream out = response.getOutputStream();
 
int len=0;
byte[] buffer = new byte[1024];
while((len=in.read(buffer))>0) {
out.write(buffer,0,len);
}
in.close();
out.close();
}


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

}

javaweb下載文件模板