11 Servlet——cookie三天免登陆

先看看项目流程

从主页开始的首次成功登陆的运行流程：index.jsp->CookieServlet（检查是否有cookie记录，如果没有记录跳转登录页面）->PageServlet（登录页面）->LoginServlet（从上个页面获取账号密码，调用service做校验，如果账号密码均正确，设置cookie并跳转主页）->MainServlet（主页）

从主页开始的3天内免登陆流程：index.jsp->CookieServlet（检查是否有cookie记录（uid），如有则调用service校验该用户是否存在，如果存在，跳转主页面）->MainServlet（主页面）

Cookie信息校验

　　编写CookieServlet

• 　　判断请求中是否携带正确的Cookie信息
• 　　如果有则校验Cookie信息是否正确
• 　　　　如果校验正确则直接响应主页面（MainServlet）给用户
• 　　　　如果校验不正确则响应登录页面（PageServlet）给用户
• 　　如果没有则请求转发给登录页面

注意：cookie中存的是用户的uid而不是账号密码，这样比较安全

CookieServlet:

package com.xiaohei.servlet;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.xiaohei.pojo.User;
import com.xiaohei.service.CookieService;
import com.xiaohei.service.LoginService;
import com.xiaohei.service.impl.CookieServiceImpl;
import com.xiaohei.service.impl.LoginServiceImpl;

/**
 * Servlet implementation class CookieServlet
 */
public class CookieServlet extends HttpServlet {
	@Override
	protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		//设置请求编码
		req.setCharacterEncoding("utf-8");
		//设置响应类型及编码
		resp.setContentType("text/html;charset=utf-8");
		//获取请求
			//判断是否有cookie
			Cookie[] cks = req.getCookies();
			//处理请求
			if(null!=cks) {
				//从cookie中获取uid
				String uid = "";
				for(Cookie c : cks) {
					if("uid".equals(c.getName())) {
						uid = c.getValue();
					}
				}
				//校验用户是否存在（使用uid）
				CookieService ls = new CookieServiceImpl();
				User u = ls.checkUidService(uid);
				if(null!=u) {//存在，跳转主页
					resp.sendRedirect("main");
					return;
				}else {//不存在，跳转登录页面
					req.getRequestDispatcher("/page").forward(req, resp);
					return;
				}
			}else {//没有cookie，跳转登录页面
				req.getRequestDispatcher("/page").forward(req, resp);
				return;
			}
			
					
	}
}

　　

CookieServiceImpl

public class CookieServiceImpl implements CookieService{

	//校验用户是否存在
		@Override
		public User checkUidService(String uid) {
			CookieDao dao = new CookieDaoImpl();
			User user = dao.checkUid(uid);
			return user;
		}

}

　　

CookieDaoImpl

public class CookieDaoImpl implements CookieDao{
	@Override
	public User checkUid(String uid) {
		User user = null;
		try(Connection conn = JDBCUtil.getConnection();) {
			String sql = "select * from t_user where uid = ? ";
			PreparedStatement ps = conn.prepareStatement(sql);
			ps.setString(1, uid);
			ResultSet set = ps.executeQuery();
			while(set.next()) {
				user = new User();
				int id = set.getInt("uid");
				String username = set.getString("uname");
				String password = set.getString("pwd");
				user.setUid(id);
				user.setUsername(username);
				user.setPassword(password);
				return user;
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return null;
	}

}

　　

LoginServlet 添加Cookie

protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
			//设置请求编码
			req.setCharacterEncoding("utf-8");
			//设置响应编码
			resp.setContentType("text/html;charset=utf-8");
			//获取请求数据
				username = req.getParameter("uname");
				password = req.getParameter("pwd");
			//处理请求
				LoginService ls = new LoginServiceImpl();
				User user = ls.checkLoginService(username, password);
			//响应
			if(null != user) {
				//创建cookie，实现3天免登陆
					//我们不直接存账号密码，而是存用户的uid
					Cookie c = new Cookie("uid",user.getUid()+"");
					//设置有效期为3天
					c.setMaxAge(3*24*3600);
					//设置指定url
					c.setPath("/200222-CookieLogin/ck");
					//添加
					resp.addCookie(c);
				String username = user.getUsername();
				String pwd = user.getPassword();
				resp.sendRedirect("main");
				return;
			}else {
				//请求转发
				req.setAttribute("msg", "账号或密码错误");
				req.getRequestDispatcher("page").forward(req, resp);
				return;
			}
		}