1.在index.jsp中写入以下代码
<form method="post" action="demo3" enctype="multipart/form-data"> ???选择一个文件: ???<input type="file" name="uploadFile"/> ???<br/><br/> ???<input type="submit" value="上传"/></form>
2.在src中创建ServletDemo3类
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;//此三个包为 正常包以外 额外需要下载导入
public class ServletDemo3 extends HttpServlet { ???private static final long serialVersionUID = 1L; ???// 上传文件存储目录 ???private static final String UPLOAD_DIRECTORY = "upload"; ???// 上传配置 ???private static final int MEMORY_THRESHOLD ??= 1024 * 1024 * 3; ?// 3MB ???private static final int MAX_FILE_SIZE ?????= 1024 * 1024 * 40; // 40MB ???private static final int MAX_REQUEST_SIZE ??= 1024 * 1024 * 50; // 50MB ???/** ????* 上传数据及保存文件 ????*/ ???protected void doPost(HttpServletRequest request, ?????????????????????????HttpServletResponse response) throws ServletException, IOException { ???????// 检测是否为多媒体上传 ???????if (!ServletFileUpload.isMultipartContent(request)) { ???????????// 如果不是则停止 ???????????PrintWriter writer = response.getWriter(); ???????????writer.println("Error: 表单必须包含 enctype=multipart/form-data"); ???????????writer.flush(); ???????????return; ???????} ???????// 配置上传参数 ???????DiskFileItemFactory factory = new DiskFileItemFactory(); ???????// 设置内存临界值 - 超过后将产生临时文件并存储于临时目录中 ???????factory.setSizeThreshold(MEMORY_THRESHOLD); ???????// 设置临时存储目录 ???????factory.setRepository(new File(System.getProperty("java.io.tmpdir"))); ???????ServletFileUpload upload = new ServletFileUpload(factory); ???????// 设置最大文件上传值 ???????upload.setFileSizeMax(MAX_FILE_SIZE); ???????// 设置最大请求值 (包含文件和表单数据) ???????upload.setSizeMax(MAX_REQUEST_SIZE); ???????// 中文处理 ???????upload.setHeaderEncoding("UTF-8"); ???????// 构造临时路径来存储上传的文件 ???????// 这个路径相对当前应用的目录 ???????String uploadPath = request.getServletContext().getRealPath("./") + File.separator + UPLOAD_DIRECTORY; ???????// 如果目录不存在则创建 ???????File uploadDir = new File(uploadPath); ???????if (!uploadDir.exists()) { ???????????uploadDir.mkdir(); ???????} ???????try { ???????????// 解析请求的内容提取文件数据 ???????????@SuppressWarnings("unchecked") ???????????List<FileItem> formItems = upload.parseRequest(request); ???????????if (formItems != null && formItems.size() > 0) { ???????????????// 迭代表单数据 ???????????????for (FileItem item : formItems) { ???????????????????// 处理不在表单中的字段 ???????????????????if (!item.isFormField()) { ???????????????????????String fileName = new File(item.getName()).getName(); ???????????????????????String filePath = uploadPath + File.separator + fileName; ???????????????????????File storeFile = new File(filePath); ???????????????????????// 在控制台输出文件的上传路径 ???????????????????????System.out.println(filePath); ???????????????????????// 保存文件到硬盘 ???????????????????????item.write(storeFile); ???????????????????????request.setAttribute("message", ???????????????????????????????"文件上传成功!"); ???????????????????} ???????????????} ???????????} ???????} catch (Exception ex) { ???????????request.setAttribute("message", ???????????????????"错误信息: " + ex.getMessage()); ???????} ???????// 跳转到 message.jsp ???????request.getServletContext().getRequestDispatcher("/message.jsp").forward( ???????????????request, response); ???} ???}3.在WEB-INF进行配置文件
???<servlet> ???????<servlet-name>servletDemo3</servlet-name> ???????<servlet-class>com.neunb.servlet.ServletDemo3</servlet-class> ???</servlet> ???<servlet-mapping> ???????<servlet-name>servletDemo3</servlet-name> ???????<url-pattern>/demo3</url-pattern> ???</servlet-mapping>
4.创建message.jsp 显示上传结果
<html><head> ???<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> ???<title>文件上传结果</title></head><body> ???<h2>${message}</h2></body></html>5.上传文件运行结果
jsp使用servlet实现文件上传
原文地址：http://www.cnblogs.com/coderL/p/7522431.html