AJAX+JSP实现基于WEB的文件上传的进度控制(2)
2.1.3. 后台服务类（BackGroundService）BackGroundService这个Servlet类负责接收Form Post数据、回应状态轮询请求、处理取消文件上传的请求。 尽管可以把这些功能相互分离开来，但为了简单明了，还是将它们放到Servlet中，只是由不同的方法进行分割。 源代码如下：
/** * 本例程演示了通过Web上传文件过程中的进度显示。您可以对本例程进行任何修改和使用。 * 如果需要转载本例程，请您注明作者。 * * 作者： 刘作晨 * EMail:liuzuochen@gmail.com */package liuzuochen.sample.upload;/** * Title: 后台服务 * * Description: 为客户端提供上传及文件传输状态查询服务 * */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.*;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); } /** * 从文件路径中取出文件名 */ private String takeOutFileName(String filePath) { int pos = filePath.lastIndexOf(File.separator); if (pos > 0) { return filePath.substring(pos + 1); } else { return filePath; } } /** * 从request中取出FileUploadStatus Bean */ public static FileUploadStatus getStatusBean( HttpServletRequest request) { BeanControler beanCtrl = BeanControler.getInstance(); return beanCtrl.getUploadStatus(request.getRemoteAddr()); } /** * 把FileUploadStatus Bean保存到类控制器BeanControler */ public static void saveStatusBean( HttpServletRequest request, FileUploadStatus statusBean) { statusBean.setUploadAddr(request.getRemoteAddr()); BeanControler beanCtrl = BeanControler.getInstance(); beanCtrl.setUploadStatus(statusBean); } /** * 删除已经上传的文件 */ 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("删除已上传的文件"); saveStatusBean(request, satusBean); } /** * 上传过程中出错处理 */ private void uploadExceptionHandle( HttpServletRequest request, String errMsg) throws ServletException, IOException { //首先删除已经上传的文件 deleteUploadedFile(request); FileUploadStatus satusBean = getStatusBean(request); satusBean.setStatus(errMsg); saveStatusBean(request, satusBean); } /** * 初始化文件上传状态Bean */ private FileUploadStatus initStatusBean(HttpServletRequest request) { FileUploadStatus satusBean = new FileUploadStatus(); satusBean.setStatus("正在准备处理"); satusBean.setUploadTotalSize(request.getContentLength()); satusBean.setProcessStartTime(System.currentTimeMillis()); satusBean.setBaseDir(request.getContextPath() + UPLOAD_DIR); return satusBean; } /** * 处理文件上传 */ private void processFileUpload(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { DiskFileItemFactory factory = new DiskFileItemFactory(); //设置内存缓冲区，超过后写入临时文件 factory.setSizeThreshold(10240000); //设置临时文件存储位置 factory.setRepository(new File(request.getRealPath("/upload/temp"))); ServletFileUpload upload = new ServletFileUpload(factory); //设置单个文件的最大上传值 upload.setFileSizeMax(102400000); //设置整个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); //获得返回url for (int i = 0; i < items.size(); i++) { FileItem item = (FileItem) items.get(i); if (item.isFormField()) { forwardURL = item.getString(); break; } } //处理文件上传 for (int i = 0; i < items.size(); i++) { FileItem item = (FileItem) items.get(i); //取消上传 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); //更新上传文件列表 FileUploadStatus satusBean = getStatusBean(request); satusBean.getUploadFileUrlList().add(fileName); saveStatusBean(request, satusBean); Thread.sleep(500); } } } catch (FileUploadException e) { uploadExceptionHandle(request, "上传文件时发生错误:" + e.getMessage()); } catch (Exception e) { uploadExceptionHandle(request, "保存上传文件时发生错误:" + e.getMessage()); } if (forwardURL.length() == 0) { forwardURL = DEFAULT_UPLOAD_FAILURE_URL; } request.getRequestDispatcher(forwardURL).forward(request, response); } /** * 回应上传状态查询 */ 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()); } /** * 处理取消文件上传 */ 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); } } }} 2.1.4. 文件上传状态控制类（BeanControler）
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