/**
 * 需要解決的問(wèn)題：
 * 1 必須要把文件存放到WEB-INF目錄下，避免用戶(hù)看到
 * 2 文件名相關(guān)問(wèn)題
 * 1 有的瀏覽器會(huì)傳遞絕對(duì)路徑到name中，我們只需要進(jìn)行拆分即可
 * 2文件重名問(wèn)題，我們可以使用uuid
 * 3文件名亂碼問(wèn)題，我們已經(jīng)解決了。即request.setCharacterEncoding("utf-8");
 * 3 文件打散問(wèn)題
 * 1通過(guò)首字符打散
 * 2通過(guò)時(shí)間打散
 * 3通過(guò)hash打散
 * 4上傳文件大小限制
 * 1單個(gè)文件上傳大小限制
 * 2總文件上傳大小限制
 * 設(shè)置這兩個(gè)參數(shù)時(shí)，我們必須在沒(méi)有解析之前執(zhí)行。
 * 5 緩存大小與臨時(shí)目錄
 * 
 * 
 * 
 **/
public class FileUploadServlet extends HttpServlet {
 public void doPost(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {
 request.setCharacterEncoding("utf-8");
 response.setContentType("text/html;charset=utf-8");
 /**
 * 我們使用commmons的小工具來(lái)進(jìn)行編碼
 * 設(shè)置jsp頁(yè)面的enctype= “multipart/form-data“;
 * 1 創(chuàng)建FileItem工廠
 * 2創(chuàng)建ServletFileUpload對(duì)象
 * 3 解析request得到FileItem
 * 4對(duì)FileItem進(jìn)行操作
 **/ 
 String path = request.getSession().getServletContext().getRealPath("/WEB-INF");
 //解決緩存大小，要不然你的內(nèi)存會(huì)爆的。
 DiskFileItemFactory diskFileItemFactory = new DiskFileItemFactory(1024 * 10,new File(path + "/" + "tmp2") );
 ServletFileUpload fileUpload = new ServletFileUpload(diskFileItemFactory);
 
 List<FileItem> l = null;
 try {
 l = fileUpload.parseRequest(request);
 
 FileItem f2 = l.get(0);
 
 //解決文件存放在WEN_INF目錄下問(wèn)題
 
 path = path + "/tmp";
 
 //解決瀏覽器傳遞絕對(duì)路徑問(wèn)題
 String name = f2.getName();
 
 int i = name.lastIndexOf("/");
 if(i != -1) {
 name = name.substring(i);
 }
 
 //解決文件重名問(wèn)題
 name = (UUID.randomUUID().toString().replace("-","").trim()) + name;
 
 
 //文件打散問(wèn)題解決方法演示之hash打散
 int has = name.hashCode();
 //轉(zhuǎn)換位16進(jìn)制位，我們使用前兩個(gè)值來(lái)判斷
 
 String hex = Integer.toHexString(has);
 path = path + "/" + hex.charAt(0) + "/" + hex.charAt(2) ;
 File file = new File(path);
 if(! file.exists()) {
 file.mkdirs();
 }
 
 f2.write(new File(path + "/" + name));
 request.setAttribute("msg","恭喜你，上傳成功了！");
 request.getRequestDispatcher("/index.jsp").forward(request, response);
 
 } catch (Exception e) {
 request.setAttribute("msg",e.getMessage());
 request.getRequestDispatcher("/index.jsp").forward(request, response);
 }
 }
}

public void doGet(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {
 /**
 * 設(shè)置兩個(gè)響應(yīng)頭
 * 1Content-Type：你傳遞給客戶(hù)端的文件是什么MIME類(lèi)型
 * 2Content-Disposition：它的默認(rèn)值為inline，表示在瀏覽器窗口中打開(kāi)！attachment;filename=xxx
 * 
 * 需要解決的的問(wèn)題：
 * 1 下載文件名中文亂碼問(wèn)題
 * 解決方法：
 * 針對(duì)不同的瀏覽器使用不同的編碼方式 火狐瀏覽器使用的是Base64編碼，其他瀏覽器一般都是使用url編碼
 **/
 String mimeType = request.getSession().getServletContext().getMimeType("\\WEB-INF\\tmp\\2\\5\\"
 + "87bd61a4b7c346a5a2e6c072de84acda5.JdbcUtils處理多線程并發(fā)訪問(wèn)問(wèn)題.avi");
 //解決文件名亂碼問(wèn)題
 String filename = "87bd61a4b7c346a5a2e6c072de84acda5.JdbcUtils處理多線程并發(fā)訪問(wèn)問(wèn)題.avi";
 filename = encoding(filename, request);
 //兩個(gè)請(qǐng)求頭
 response.setHeader("Content-Type",mimeType);
 response.setHeader("Content-Disposition","attachment;filename=" + filename);
 ServletOutputStream out = response.getOutputStream();
 String path = request.getSession().getServletContext().getRealPath("\\WEB-INF\\tmp\\2\\5\\"
 + "87bd61a4b7c346a5a2e6c072de84acda5.JdbcUtils處理多線程并發(fā)訪問(wèn)問(wèn)題.avi");
 File file = new File(path);
 
 FileInputStream inputStream = new FileInputStream(file);
 
 IOUtils.copy(inputStream, out, 1024*1024);
 
 }
 
 private String encoding(String filename,HttpServletRequest req) throws UnsupportedEncodingException {
 String user_agent = req.getHeader("User-Agent");
 String encodingFileName = null;
 if(user_agent.contains("Firefox")) {
 //按道理來(lái)說(shuō)應(yīng)該使用 BASE64Encoder進(jìn)行編碼，但是不知道為什么不能成功
 /*BASE64Encoder base64Encoder = new BASE64Encoder();
 encodingFileName = "=?utf-8?B?"
  + base64Encoder.encode(filename.getBytes("utf-8"))
  + "?=";*/
 //那我們只能使用這種方式了
 encodingFileName = new String(filename.getBytes("UTF-8"), "ISO-8859-1");
 }
 else {
 encodingFileName = URLEncoder.encode(filename,"utf-8");
 }
 return encodingFileName;
 }
 
}