jsp 使用Common-FileUpload組件檔案上傳及限制上傳類型，
1、將commons-fileupload-1.3.3.jar複製到Web應用的lib檔案夾下，在WebRoot目錄下建立limit.jsp頁面，在該頁面中添加一個檔案域的表單，設定類型為 multipart/form-data。代碼如下：
<body> <h2>上傳圖書課件</h2> <form action="LimitFile" name="one" enctype="multipart/form-data" method="post"> 選擇一個rar檔案： <input type="file" name="fileupload" value="upload" /> <input type="submit" value="上傳"> <input type="reset" value="取消"> </form> </body>
上述代碼指定提交後將請求提交給LimitFile處理，LimitFile(Servlet)用來處理上傳檔案及判斷檔案類型是否匹配，顯示上傳結果。
2、建立名為LimitFile的Servlet，並在doPost()方法中編寫實現代碼，如下所示：
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("utf-8"); response.setCharacterEncoding("utf-8"); response.setContentType("text/html"); PrintWriter out = response.getWriter(); String uploadpath = ""; DiskFileItemFactory factory = new DiskFileItemFactory(); //設定是否使用臨時檔案儲存解析出來的資料的那個臨界值，該方法傳入參數的單位是位元組。 factory.setSizeThreshold(30 * 1024); //用於設定setSizeThreshold()方法中提到的臨時檔案的存放目錄，這裡要求使用絕對路徑。 factory.setRepository(factory.getRepository()); ServletFileUpload upload = new ServletFileUpload(factory); List list = null; try{ list = upload.parseRequest(request); String[] limit = new String[]{".jpg", ".gif", ".png", ".bmp"}; //定義限制的檔案類型 SuffixFileFilter filter = new SuffixFileFilter(limit); //擷取SuffixFileFilter執行個體 Iterator iterator = list.iterator(); while(iterator.hasNext()){ FileItem item =(FileItem)iterator.next(); if(!item.isFormField()){ String filePath = item.getName(); if(filePath != null){ File filename= new File(filePath); File uploadFile = new File(request.getSession().getServletContext().getRealPath("/") + "upload"); uploadpath = uploadFile.getAbsolutePath()+File.pathSeparator + uploadpath; //因為路徑後面多了個";"號，所以要去掉 uploadpath = uploadpath.substring(0, uploadpath.length()-1); File saveFile = new File(uploadpath,filename.getName()); boolean flag = filter.accept(saveFile); if(flag){ out.print("禁止上傳傳圖片檔案"); break; }else{ try { item.write(saveFile); out.print("檔案上傳成功"); } catch (Exception e) { out.print("檔案上傳失敗了"); e.printStackTrace(); } } } } } }catch(FileUploadException e){ e.printStackTrace(); } }
上述代碼在位元組串數組limit中定義了不允許上傳的檔案類型，然後將該數組傳遞給SuffixFileFilter類的建構函式。在通過該類的accept()方法驗證當前上傳的檔案是否符合條件。最後將檔案儲存到項目的upload目錄下。
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