之前没怎么用过这个，这次项目中用到了，于是总结一下：

应该说主要注意三方面：

1、写一个servlet

2、在web.xml中配置这个servlet

3、页面上调用这个servlet

第一：

写一个servlet，当然要继承javax.servlet.http.HttpServlet，重写post或者get方法（看需要），这个servlet的思想就是将要下载的文件写到文件流中去，而这个文件输出流就是HttpServletResponse对象的输出流，如下所示：

public class DownloadServlet extends HttpServlet{
 
 
 public void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException
 {
  try
  {
   String downFilename=request.getParameter("curfile");
   String filepath=request.getParameter("path");
        response.setContentType("text/plain");
        response.setHeader("Location",downFilename);
        response.setHeader("Content-Disposition", "p_w_upload; filename=" + downFilename);
        OutputStream outputStream = response.getOutputStream();
        InputStream inputStream = new FileInputStream(filepath+downFilename);
        byte[] buffer = new byte[1024];
        int i = -1;
        while ((i = inputStream.read(buffer)) != -1) {
         outputStream.write(buffer, 0, i);
        }
        outputStream.flush();
        outputStream.close();
  }catch(FileNotFoundException e1)
  {
   System.out.println("没有找到您要的文件");
  }
  catch(Exception e)
  {
   System.out.println("系统错误，请及时与管理员联系");
  }
    }
 
 
 public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException
 {
  doPost(request,response);
 }

}

web.xml配置:

  download
  com.dichain.common.tools.DownloadServlet
 

  download   
  /Download
 

jsp中调用servlet弹出一个下载对话框：

window.open ('Download?curfile='+curfile+'&path='+path,'newwindow','height=30,width=40,top='+yy+',left='+xx+',toolbar=no,menubar=no,scrollbars=no, resizable=no,location=no, status=no');