Java中，当表单含有文件上传时，提交数据的如何读取

来源：互联网发布：中信证券软件编辑：程序博客网时间：2024/05/18 03:31

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-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();
}
}
}

// 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