当提交表单里包含文件上传的时候,即Form的enctype属性值为multipart/form-data时,后台是无法像普通表单那样通过request.getParameter来获取用户提交的数据的。(说实话,我经常因为忘记这个问题而浪费好多调查时间。)
这时候,当然可以通过解析提交到服务器的数据流来得到数据了,但是这样不但麻烦而且容易出错。
最好的方式是使用第三方的jar包获取数据,这方面有很多现成的成熟优秀的jar包。最常用的时以下三个:
apache的commons-fileupload : http://commons.apache.org/fileupload/
O'Reilly的cos: http://www.servlets.com/cos/index.html
jspsmart的SmartUpload:官方不提供下载了,google搜吧。
1. common-upload示例代码: [java] view plain copy // 判断enctype属性是否为multipart/form-data boolean isMultipart = ServletFileUpload.isMultipartContent(request); // Create a factory for disk-based file items DiskFileItemFactory factory = new DiskFileItemFactory(); // 当上传文件太大时,因为虚拟机能使用的内存是有限的,所以此时要通过临时文件来实现上传文件的保存 // 此方法是设置是否使用临时文件的临界值(单位:字节) factory.setSizeThreshold(yourMaxMemorySize); // 与上一个结合使用,设置临时文件的路径(绝对路径) factory.setRepository(yourTempDirectory); // Create a new file upload handler ServletFileUpload upload = new ServletFileUpload(factory); // 设置上传内容的大小限制(单位:字节) upload.setSizeMax(yourMaxRequestSize); // Parse the request List<?> items = upload.parseRequest(request); Iterator iter = items.iterator(); while (iter.hasNext()) { FileItem item = (FileItem) iter.next(); if (item.isFormField()) { //如果是普通表单字段 String name = item.getFieldName(); String value = item.getString(); ... } else { //如果是文件字段 String fieldName = item.getFieldName(); String fileName = item.getName(); String contentType = item.getContentType(); boolean isInMemory = item.isInMemory(); long sizeInBytes = item.getSize(); ... // Process a file upload if (writeToFile) { File uploadedFile = new File(...); item.write(uploadedFile); } else { InputStream uploadedStream = item.getInputStream(); ... uploadedStream.close(); } } } 2. cos示例代码: [java] view plain copy // 设置大小限制(单位:字节) final int permitedSize = 314572800; try { String type = ""; String name = ""; String originalFilename = ""; String extension1 = ""; String extension2 = ""; String filename = ""; //上传目录 String strDirectory = "files"; String uploadPath = request.getRealPath("//WEB-INF//"+strDirectory+"//"); // 获取句柄 MultipartRequest multipartRequest = new MultipartRequest(request, uploadPath, permitedSize, "ISO-8859-1", new DefaultFileRenamePolicy()); // 取得文件 Enumeration files = multipartRequest.getFileNames(); // 取得文件详细信息 while (files.hasMoreElements()) { name = (String)files.nextElement(); type = multipartRequest.getContentType(name); filename = multipartRequest.getFilesystemName(name); originalFilename = multipartRequest.getOriginalFileName(name); File currentFile = multipartRequest.getFile(name); ... } // 取得其它非文件字段 Enumeration params = multipartRequest.getParameterNames(); while (params.hasMoreElements()) { String name = (String)params.nextElement(); String value = multi.getParameter(name); ... } } catch (Exception exception) { response.sendError(response.SC_METHOD_NOT_ALLOWED); } finally { if (out != null) {out.close();} } 3. SmartUpload示例代码: [java] view plain copy smartupload mysmartupload = new smartupload(); mysmartupload.initialize(this.getServletConfig(), request, response); // 设置文件大小限制(单位:字节) mysmartupload.setMaxFileSize(10000000); // 设置总上传数据总大小(单位:字节) mysmartupload.setTotalMaxFileSize(20000000); // 设置允许的文件扩展名 mysmartupload.setAllowedFilesList("jpg,png,gif,bmp,jpeg"); // 设置不允许的文件扩展名 mysmartupload.setDeniedFilesList("exe,bat,jsp,htm,html,,"); try { mysmartupload.upload(); } catch (smartuploadException e1) { e1.printStackTrace(); } // 读取其它非文件上传字段 com.jspsmart.upload.Request req = mysmartupload.getRequest(); String title = req.getParameter("dest"); // 保存文件 for (int i = 0; i < mysmartupload.getFiles().getCount(); i++) { com.jspsmart.upload.File file = mysmartupload.getFiles().getFile(i); if (file.isMissing()) continue; try { file.saveAs("yourSavePath" + file.getFileName()); } catch (smartuploadException e) { e.printStackTrace(); } }