【JavaWeb实现自动登录】

前端

	<div class="submit_btn">
    	<button type="button" id="btn_sub">登录</button>
        <div class="auto_login">
        	<input type="checkbox" name="remember" value="remember" class="checkbox">
        	<span>自动登录</span>
        </div>        				
    </div>

Servlet

		//在登录成功时，判断选中状态
		String remember = request.getParameter("remember");
    	if("remember".equals(remember)){//如果选中了自动登录
        	String uri = request.getContextPath() + "/";//存储路径
            int expiry = 60*60*24*15;//存储时间
            Cookie c = new Cookie("uname",user.getUsername());//存储内容
     		c.setPath(uri);
            c.setMaxAge(expiry);
            response.addCookie(c);//添加到浏览器的Cookie
            c = new Cookie("upwd", user.getPassword());
            c.setPath(uri);
            c.setMaxAge(expiry);
            response.addCookie(c);
        }

判断完选中状态后，将登录查询的信息保存到session：session.setAttribute("user",u);

过滤器Filter

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import java.io.IOException;


@WebFilter("/*")
public class AutoLoginFilter implements Filter {
    public void destroy() {
    }

    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
        HttpServletRequest request = (HttpServletRequest)req;

        //1. 未进入登录状态-session无标志位
        //如果user的session为空说明未登录
        HttpSession session = request.getSession();
        boolean flag1 = session.getAttribute("user") == null;
        //2. Cookie有账号|密码
        String uname = null;
        String upwd = null;
        Cookie[] cookies = request.getCookies();//获取cookie
        if(cookies!=null){//如果获取到了
            boolean flag2 = false;
            for(Cookie c : cookies){//遍历
            	//将登录时保存的用户名和密码拿出来，并将flag2设置为true
                if(c.getName().equals("uname")){
                    uname = c.getValue();
                }else if(c.getName().equals("upwd")){
                    upwd = c.getValue();
                }
                if(uname!=null && upwd!=null){
                    flag2 = true;
                    break;
                }
            }
            //如果没有登录flag1=true且在cookie中找到了账号密码，就进行登录
            if(flag1&&flag2){
                UserDao dao = new UserDaoImpl();
                User u = dao.findByUsernameAndPassowrd(uname, upwd);
                if (u != null){
                    session.setAttribute("user",u);
                }
            }
            chain.doFilter(req, resp);//放行
        }else{
            chain.doFilter(req, resp);//放行
        }
    }

    public void init(FilterConfig config) throws ServletException {

    }

}

到这里实现了自动登录功能

最后不要忘记，点击退出登录时清空seession的同时也要要清空cookie

		//1、销毁session
        request.getSession().invalidate();
        //2、清空Cookie
        String uri = request.getContextPath() + "/";
        Cookie c = new Cookie("uname","");
        c.setPath(uri);
        c.setMaxAge(0);
        response.addCookie(c);
        c = new Cookie("upwd","");
        c.setPath(uri);
        c.setMaxAge(0);
        response.addCookie(c);
        //2、跳转页面
        response.sendRedirect(request.getContextPath()+"/login.html");