JSP新闻系统之八 Servlet

实用Servlet实现登陆验证

package com.news.servlet;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;import javax.servlet.http.HttpSession;import com.news.dao.UserDao;import com.news.dao.impl.UserDaoImpl;import com.news.entity.User;public class LoginServlet extends HttpServlet {/** * 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 {HttpSession session = request.getSession();PrintWriter out = response.getWriter();String rand = (String)session.getAttribute("rand");      String username = request.getParameter("username");   String userpwd = request.getParameter("userpwd");   String srand = request.getParameter("rand");      if(!rand.equals(srand)){   out.println("<script>alert('验证码错误！！');location.href='login.jsp';</script>");   return;   }      UserDao userDao = new UserDaoImpl();      boolean flag = userDao.checkLogin(username,userpwd);      if(flag){   User user = new User();   user.setUsername(username);   session.setAttribute("user",user);   response.sendRedirect("index.jsp");   }   else{   response.sendRedirect("login.jsp");   }}}