package shubin.sample.upload;

/**
 * Title: 后臺服務
 * * Description: 為客戶端提供上傳及文件傳輸狀態查詢服務
 *
 */
import java.io.File;
import java.io.IOException;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
public class BackGroundService extends javax.servlet.http.HttpServlet implements
         javax.servlet.Servlet {
     public static final String UPLOAD_DIR = "/upload";
     public static final String DEFAULT_UPLOAD_FAILURE_URL = "./result.jsp";
     public BackGroundService() {
         super();
     }
     protected void doGet(HttpServletRequest request,
                          HttpServletResponse response) throws ServletException,
             IOException {
         doPost(request, response);
     }
     /**
      * 從文件路徑中取出文件名
      */
     private String takeOutFileName(String filePath) {
         int pos = filePath.lastIndexOf(File.separator);
         if (pos > 0) {
             return filePath.substring(pos + 1);
         } else {
             return filePath;
         }
     }
     /**
      * 從request中取出FileUploadStatus Bean
      */
     public static FileUploadStatus getStatusBean(
             HttpServletRequest request) {
         BeanControler beanCtrl = BeanControler.getInstance();
         return beanCtrl.getUploadStatus(request.getRemoteAddr());
     }
     /**
      * 把FileUploadStatus Bean保存到類控制器BeanControler
      */
     public static void saveStatusBean(
             HttpServletRequest request,
             FileUploadStatus statusBean) {
         statusBean.setUploadAddr(request.getRemoteAddr());
         BeanControler beanCtrl = BeanControler.getInstance();
         beanCtrl.setUploadStatus(statusBean);
     }
     /**
      * 刪除已經上傳的文件
      */
     private void deleteUploadedFile(HttpServletRequest request) {
         FileUploadStatus satusBean = getStatusBean(request);
         for (int i = 0; i < satusBean.getUploadFileUrlList().size(); i++) {
             File uploadedFile = new File(request.getRealPath(UPLOAD_DIR) +
                                          File.separator +
                                          satusBean.getUploadFileUrlList().
                                          get(i));
             uploadedFile.delete();
         }
         satusBean.getUploadFileUrlList().clear();
         satusBean.setStatus("刪除已上傳的文件");
         saveStatusBean(request, satusBean);
     }
     /**
      * 上傳過程中出錯處理
      */
     private void uploadExceptionHandle(
             HttpServletRequest request,
             String errMsg) throws ServletException, IOException {
         //首先刪除已經上傳的文件
         deleteUploadedFile(request);
         FileUploadStatus satusBean = getStatusBean(request);
         satusBean.setStatus(errMsg);
         saveStatusBean(request, satusBean);
     }
     /**
      * 初始化文件上傳狀態Bean
      */
     private FileUploadStatus initStatusBean(HttpServletRequest
             request) {
         FileUploadStatus satusBean = new FileUploadStatus();
         satusBean.setStatus("正在準備處理");
         satusBean.setUploadTotalSize(request.getContentLength());
         satusBean.setProcessStartTime(System.currentTimeMillis());
         satusBean.setBaseDir(request.getContextPath() + UPLOAD_DIR);
         return satusBean;
     }
     /**
      * 處理文件上傳
      */
     private void processFileUpload(HttpServletRequest request,
                                    HttpServletResponse response) throws
             ServletException, IOException {
         DiskFileItemFactory factory = new DiskFileItemFactory();
         //設置內存緩沖區，超過后寫入臨時文件
         factory.setSizeThreshold(10240000);
         //設置臨時文件存儲位置
         factory.setRepository(new File(request.getRealPath("/upload/temp")));
         ServletFileUpload upload = new ServletFileUpload(factory);
         //設置單個文件的最大上傳值
         upload.setFileSizeMax(102400000);
         //設置整個request的最大值
         upload.setSizeMax(102400000);
         upload.setProgressListener(new FileUploadListener(request));
         //保存初始化后的FileUploadStatus Bean
         saveStatusBean(request, initStatusBean(request));
         String forwardURL = "";
         try {
             List items = upload.parseRequest(request);
             //獲得返回url
             for (int i = 0; i < items.size(); i++) {
                 FileItem item = (FileItem) items.get(i);
                 if (item.isFormField()) {
                     forwardURL = item.getString();
                     break;
                 }
             }
             //處理文件上傳
             for (int i = 0; i < items.size(); i++) {
                 FileItem item = (FileItem) items.get(i);
                 //取消上傳
                 if (getStatusBean(request).getCancel()) {
                     deleteUploadedFile(request);
                     break;
                 }
                 //保存文件
                 else if (!item.isFormField() && item.getName().length() > 0) {
                     String fileName = takeOutFileName(item.getName());
                     File uploadedFile = new File(request.getRealPath(UPLOAD_DIR) +
                                                  File.separator + fileName);
                     item.write(uploadedFile);
                     //更新上傳文件列表
                     FileUploadStatus satusBean =
                             getStatusBean(request);
                     satusBean.getUploadFileUrlList().add(fileName);
                     saveStatusBean(request, satusBean);
                     Thread.sleep(500);
                 }
             }
         } catch (FileUploadException e) {
             uploadExceptionHandle(request, "上傳文件時發生錯誤:" + e.getMessage());
         } catch (Exception e) {
             uploadExceptionHandle(request, "保存上傳文件時發生錯誤:" + e.getMessage());
         }
         if (forwardURL.length() == 0) {
             forwardURL = DEFAULT_UPLOAD_FAILURE_URL;
         }
         request.getRequestDispatcher(forwardURL).forward(request, response);
     }
     /**
      * 回應上傳狀態查詢
      */
     private void responseStatusQuery(HttpServletRequest request,
                                               HttpServletResponse response) throws
             IOException {
         response.setContentType("text/xml");
         response.setHeader("Cache-Control", "no-cache");
         FileUploadStatus satusBean = getStatusBean(request);
         response.getWriter().write(satusBean.toJSon());
     }
     /**
      * 處理取消文件上傳
      */
     private void processCancelFileUpload(HttpServletRequest request,
                                          HttpServletResponse response) throws
             IOException {
         FileUploadStatus satusBean = getStatusBean(request);
         satusBean.setCancel(true);
         saveStatusBean(request, satusBean);
         responseStatusQuery(request, response);
     }
     protected void doPost(HttpServletRequest request,
                           HttpServletResponse response) throws ServletException,
             IOException {
         boolean isMultipart = ServletFileUpload.isMultipartContent(request);
         if (isMultipart) {
             processFileUpload(request, response);
         } else {
             request.setCharacterEncoding("UTF-8");
             if (request.getParameter("uploadStatus") != null) {
                 responseStatusQuery(request, response);
             }
             if (request.getParameter("cancelUpload") != null) {
                 processCancelFileUpload(request, response);
             }
         }
     }
}