Java中，当表单含有文件上传时，提交数据的如何读取 – rong

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。

其中，据评测效率最高的是COS，最慢的是SmartUpload；最常用的是common-upload；文件太大时SmartUpland会崩溃。

1. common-upload示例代码：

[java] view plaincopyprint?

// 判断enctype属性是否为multipart/form-databoolean isMultipart = ServletFileUpload.isMultipartContent(request);// Create a factory for disk-based file itemsDiskFileItemFactory 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 handlerServletFileUpload 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 uploadif (writeToFile) { File uploadedFile = new File(…); item.write(uploadedFile); } else {InputStream uploadedStream = item.getInputStream();… uploadedStream.close(); } } }

// 判断enctype属性是否为multipart/form-databoolean isMultipart = ServletFileUpload.isMultipartContent(request);// Create a factory for disk-based file itemsDiskFileItemFactory 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 handlerServletFileUpload upload = new ServletFileUpload(factory);// 设置上传内容的大小限制（单位：字节）upload.setSizeMax(yourMaxRequestSize);// Parse the requestList<?> 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 uploadif (writeToFile) {    File uploadedFile = new File(...);    item.write(uploadedFile);} else {    InputStream uploadedStream = item.getInputStream();    ...    uploadedStream.close();}    }}

2. cos示例代码：

[java] view plaincopyprint?

// 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();} }

// 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 plaincopyprint?

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(); } }

原文：http://blog.csdn.net/lian_zhihui1984/article/details/6822201敏而好学，不耻下问。