使用Servlet实现的注册登录示例，包含文件上传，注释超级详细

package servlet; import com.google.gson.Gson; import data.UserBean; import org.apache.commons.fileupload.FileItem; import org.apache.commons.fileupload.FileUploadException; import org.apache.commons.fileupload.disk.DiskFileItemFactory; import org.apache.commons.fileupload.servlet.ServletFileUpload; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.File; import java.io.IOException; import java.io.InputStream; import java.util.ArrayList; import java.util.List; @WebServlet(name = "RegisterServlet", value = "/register.do") public class RegisterServlet extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("utf-8"); response.setHeader("Content-type", "text/html;charset=UTF-8"); /*判断request 的请求方式是否为post并且contentType是否以multipart/开头 * * 如果不是说明是普通的表单提交 * */ if (!ServletFileUpload.isMultipartContent(request)) { return; } /*创建一个DiskFileItemFactory对象，这里我们使用默认配置*/ DiskFileItemFactory factory = new DiskFileItemFactory(); /*创建一个ServletFileUpload对象*/ ServletFileUpload servletFileUpload = new ServletFileUpload(factory); try { /*解析request对象，返回FileItem集合*/ List<FileItem> items = servletFileUpload.parseRequest(request); /*创建一个UserBean 用于封装用户数据*/ UserBean userBean = new UserBean(); /*该集合用于存储提交的爱好数据*/ List<String> hobbyList = new ArrayList<>(); /*遍历FileItem集合*/ for (FileItem item : items) { String filedName = item.getFieldName();//获取name属性 System.out.println("filedName=" + filedName); if (item.isFormField()) { /*处理表单项*/ String value = item.getString("utf-8"); System.out.println("value=" + value); if (filedName.equals("account")) { userBean.setAccount(value); } else if (filedName.equals("pwd")) { userBean.setPwd(value); } else if (filedName.equals("gender")) { userBean.setGender(value); } else if (filedName.equals("hobbies")) { hobbyList.add(value); } } else { /*处理文件上传*/ if (filedName.equals("img")) { /*获取上传文件的名字*/ String fileName = item.getName(); System.out.println("上传的文件名称为：" + fileName); /*获取后缀名*/ int index = fileName.lastIndexOf("."); String endWith = fileName.substring(index); System.out.println("后缀名：" + endWith); /*重新命名*/ String newFileName = System.currentTimeMillis() + endWith; System.out.println("新文件名称：" + newFileName); String path = getServletContext().getRealPath("./") + File.separator + "upload"; /*保存文件*/ File dir = new File(path); if (!dir.exists()) { System.out.println("文件夹不存在 创建"); dir.mkdir(); } String filePath = path + File.separator + newFileName; File file = new File(filePath); item.write(file); userBean.setImg(filePath); } } } userBean.setHobbies(hobbyList); System.out.println("注册完成" + userBean.toString()); /*保存注册的数据*/ List<UserBean> userList = (List<UserBean>) getServletContext().getAttribute("userList"); userList.add(userBean); /*返回注册信息*/ response.getWriter().append("<h1>"); response.getWriter().append("注册成功：" + new Gson().toJson(userBean)); response.getWriter().append("</h1>"); System.out.println("目前注册的用户个数：" + userList.size()); } catch (FileUploadException e) { e.printStackTrace(); } catch (Exception e) { e.printStackTrace(); } } }