文件上传的Serlvet类

public class FileUploadServlet extends HttpServlet {
 private static final long serialVersionUID = 1L;
 private ServletFileUpload upload;
 private final long MAXSize = 4194304*2L;//4*2MB
 private String filedir=null;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public FileUploadServlet() {
        super();
        // TODO Auto-generated constructor stub
    }
 /**
  * 设置文件上传的初始化信息
  * @see Servlet#init(ServletConfig)
  */
 public void init(ServletConfig config) throws ServletException {
  FileItemFactory factory = new DiskFileItemFactory();// Create a factory for disk-based file items
  this.upload = new ServletFileUpload(factory);// Create a new file upload handler
  this.upload.setSizeMax(this.MAXSize);// Set overall request size constraint 4194304
  filedir=config.getServletContext().getRealPath("images");
  System.out.println("filedir="+filedir);
 }
 /**
  * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
  */
 @SuppressWarnings("unchecked")
 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  // TODO Auto-generated method stub
  PrintWriter out=response.getWriter();
  try {
   List<FileItem> items = this.upload.parseRequest(request);
   if(items!=null && !items.isEmpty()){
    for (FileItem fileItem : items) {
     String filename=fileItem.getName();
     String filepath=filedir+File.separator+filename;
     System.out.println("文件保存路径为:"+filepath);
     File file=new File(filepath);
     InputStream inputSteam=fileItem.getInputStream();
     BufferedInputStream fis=new BufferedInputStream(inputSteam);
        FileOutputStream fos=new FileOutputStream(file);
        int f;
        while((f=fis.read())!=-1)
        {
           fos.write(f);
        }
        fos.flush();
        fos.close();
        fis.close();
     inputSteam.close();
     System.out.println("文件："+filename+"上传成功!");
    }
   }
   System.out.println("上传文件成功!");
   out.write("上传文件成功!");
  } catch (FileUploadException e) {
   e.printStackTrace();
   out.write("上传文件失败:"+e.getMessage());
  }
 }
}