使用servlet怎么实现一个图片上传功能

public class BackGroundLogoServlet extends HttpServlet
{
   private static final Logger m_logger=Logger.getLogger (BackGroundLogoServlet. class);
   
   @Override
   public void init(ServletConfig config) throws ServletException {
      super.init(config);
      m_logger.debug ( "BackGroundLogoServlet init.");
   }
   
   @Override
   protected void doGet(HttpServletRequest request, HttpServletResponse response)
         throws ServletException{  
      response.setContentType( "image/png");
      response.setHeader( "Access-Control-Allow-Origin", "*");
      String fileName = request.getParameter( "filename");//获取参数值titlebar_logo.png
      File file = new File( "D:\\"+ fileName);//读取D:\\titlebar_logo.png图片
      FileInputStream fis = null;
      BufferedOutputStream out= null;
      try
      {
        fis = new FileInputStream(file);
        out = new BufferedOutputStream(response.getOutputStream());
        byte[] buffer= new byte[1024];
        int len;
        while((len=fis.read(buffer))!=-1)
        {
          //read the file from local disk
          //write to client
          out.write(buffer, 0, len);   
          out.flush();
          m_logger.debug ( "background pic upload success !");
        }
      }
      catch (FileNotFoundException e)
      {
        try
        {
          response.reset();
          //set content type once again
          response.setContentType("text/html;charset=utf-8" );
          //give error message to client
          response.getWriter().println( "文件未找到" );
        }
        catch (IOException e1)
        {
          e1.printStackTrace();
        }
        e.printStackTrace();
      }
      catch (IOException e)
      {
        e.printStackTrace();
      }
      finally
      {
        try
        {
          if(fis!= null){
          fis.close();
        }
        if(out!= null){
          out.close();
        }
      }
      catch (IOException e)
      {
        e.printStackTrace();
      }
    }
      
   }