需要的jar包

jsp页面中内容

<form action="${pageContext.request.contextPath }/servlet/FileUpdate" method="post" enctype="multipart/form-data"><div align="center"><fieldset style="width:80%"><legend>上传文件</legend><br/><div align="left">上传文件1</div><div align="left"><input type="file" name="file1"/></div><div><div align='left'><input type='submit' value="上传文件"/></div></div></fieldset></div></form>

servlet

public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setContentType("text/html;charset=utf-8");PrintWriter out = response.getWriter();// Create a factory for disk-based file itemsDiskFileItemFactory factory = new DiskFileItemFactory();// Configure a repository (to ensure a secure temp location is used)ServletContext servletContext = this.getServletConfig().getServletContext();File repository = (File) servletContext.getAttribute("javax.servlet.context.tempdir");factory.setRepository(repository);// Create a new file upload handlerServletFileUpload upload = new ServletFileUpload(factory);upload.setHeaderEncoding("utf-8");// Parse the requestString saveName = "";try {List<FileItem> items = upload.parseRequest(request);for (FileItem item : items) {if(item.isFormField()){//如果只是表单中信息,不是表单文件String fieldName = item.getFieldName();String fieldValue = item.getString();out.print("<br>fieldName: "+fieldName+",--fieldValue: "+fieldValue);}else{InputStream inputStream = item.getInputStream();//得到保存文件的路径String realpath=this.getServletContext().getRealPath("update");//得到上传的文件的名字String allFilePath = item.getName();//getName()值为绝对路径！！！下面代码转换取文件名String fileName = null;int ind = allFilePath.lastIndexOf("\\");if (ind != -1) {fileName = allFilePath.substring(ind + 1);}else {fileName = allFilePath;}out.print("<br>上传的文件名: "+fileName);File file=new File(realpath + "\\" + fileName);if(file.getParentFile().exists()){file.createNewFile();//创建文件}else {file.getParentFile().mkdirs();//创建父级文件路径file.createNewFile();//创建文件}FileOutputStream fos=new FileOutputStream(file);byte[] bytes= new byte[1024];int len=0;//写入文件while((len=inputStream.read(bytes))!=-1){fos.write(bytes, 0, len);}inputStream.close();fos.close();out.print("<h3>"+allFilePath+"文件上传成功</h3>");}}} catch (FileUploadException e) {e.printStackTrace();} catch (FileNotFoundException e) {e.printStackTrace();System.out.println(saveName);}}

web.xml

<servlet><servlet-name>FileUpdate</servlet-name><servlet-class>com.oneself.shopping.servlet.FileUpdate</servlet-class>
</servlet>
<servlet-mapping><servlet-name>FileUpdate</servlet-name><url-pattern>/servlet/FileUpdate</url-pattern>
</servlet-mapping>

问题

　　java.io.FileNotFoundException: D:\update (拒绝访问。)FileOutputStream读取流的时候如果是文件夹，就会出此错误。读取的目录后面要加文件名，如下：File file=new File(realpath + "\\" + fileName);if(file.getParentFile().exists()){file.createNewFile();//创建文件}else {file.getParentFile().mkdirs();//创建父级文件路径file.createNewFile();//创建文件}FileOutputStream fos=new FileOutputStream(file);byte[] bytes= new byte[1024];int len=0;//写入文件while((len=inputStream.read(bytes))!=-1){fos.write(bytes, 0, len);}