cookie

cookie:将数据储存在客户端。 session:将数据储存在服务端，较安全

 携带sevlet a 的数据，来访问sevlet b。

@WebServlet("/a")
public class se extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException, ServletException {
        //super.doGet(req, resp);
//        List<brands> brand=new ArrayList<>();
//        brand.add(new brands(1,"三只松鼠","三只松鼠"));
//        brand.add(new brands(2,"优衣库","优衣库"));
//
//        req.setAttribute("brands",brand);
//
//        req.getRequestDispatcher("src/main/webapp/index.jsp").forward(req,resp);
        Cookie cookies=new Cookie("us","dd");
        resp.addCookie(cookies);
    }

@WebServlet("/b")
public class s extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //super.doGet(req, resp);
        Cookie[] cookies=req.getCookies();
        for(Cookie cookie:cookies){
            String name=cookie.getName();
            if("us".equals(name)){
                String value=cookie.getValue();
                System.out.println(name+value);
                break;
            }

        }
    }

细节：储存中文即cookie的存活时间

@WebServlet("/a")
public class se extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException, ServletException {
        Cookie cookies=new Cookie("us","dd");
        cookies.setMaxAge(60*60*24*7);//设置cookie的存活时间，即记住数据多久
        String value="张三";
        value= URLEncoder.encode(value,"UTF-8");//储存中文
        System.out.println(value);
        resp.addCookie(cookies);
    }



session

@WebServlet("/session1")
public class session1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //super.doGet(req, resp);
        HttpSession session=req.getSession();
        session.setAttribute("username","doudou");

    }

@WebServlet("/session2")
public class session2 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
       // super.doGet(req, resp);
        HttpSession session=req.getSession();
        Object username=session.getAttribute("username");
        System.out.println(username);

    }