java提供文件下载的方法

    String root  =  getServletContext().getRealPath( " / " );
    String path  =  request.getParameter( " path " );
    String name  =  request.getParameter( " name " );


    response.setContentType( " unknown " );
    response.addHeader( " Content-Disposition " ,  " filename=\ ""  + name +  " \ "" );


     try
     {
        java.io.OutputStream    os  = response.getOutputStream();
        java.io.FileInputStream fis = new java.io.FileInputStream(root + path + name);


        byte[] b = new byte[1024];
        int    i = 0;


        while ( (i = fis.read(b)) > 0 ) 
        {
            os.write(b, 0, i);
        }


        fis.close();
        os.flush();
        os.close();
    }
     catch  ( Exception e )
     {
    }