最简单Jsp-Servlet的MVC架构例子，适合初学者

package com.qhit; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class AdminAddAction extends HttpServlet { private AdminDao dao=new AdminDao(); /** * Constructor of the object. */ public AdminAddAction() { super(); } /** * Destruction of the servlet. <br> */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } /** * The doGet method of the servlet. <br> * * This method is called when a form has its tag value method equals to get. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request, response); } /** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to post. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("UTF-8"); response.setContentType("text/html;charset=UTF-8"); // 1.获取参数 // 2.填充bean Admin admin=new Admin(); fillAdmin(request.getParameter("adminName"), request.getParameter("adminPwd"), admin); // 3.验证 String message=validateAdmin(admin); if(!(message==null)){ request.setAttribute("msg", message); request.getRequestDispatcher("../adminAdd.jsp").forward(request, response); return; } // 4.调用dao.add if(dao.add(admin)){ request.setAttribute("msg", "保存成功"); request.getRequestDispatcher("AdminListAction").forward(request, response); } else{ request.setAttribute("msg", "保存失败"); request.getRequestDispatcher("../adminAdd.jsp").forward(request, response); } // 5.根据返回结果前向到页面 // a)成功：main.jsp // b)失败：提示信息，到adminAdd.jsp } private String validateAdmin(Admin admin) { if(admin.getAdminName().equals("")){ return "用户名不能为空。"; } if(!admin.getAdminName().matches("\\w{5,8}")){ return "用户名长度应该是5至8位长。"; } if(admin.getAdminPwd().equals("")){ return "用户密码不能为空。"; } if(!admin.getAdminPwd().matches("\\w{4,8}")){ return "用户名密码应该是5至8位长。"; } if(!(dao.get(admin.getAdminName())==null)){ return "该用户名已经被使用"; } return null;//真出口 } private String fillAdmin(String adminName,String adminPwd,Admin admin){ if(adminName==null){ admin.setAdminName(""); } else{ admin.setAdminName(adminName); } if(adminPwd==null){ admin.setAdminPwd(""); } else{ admin.setAdminPwd(adminPwd); } return null; } }