cookie_ session

One 、cookie

Solve the problem of Chinese code disorder ：

        //  solve post Request Chinese garbled code problem 
        //  It must be called before the request parameter is obtained 
        req.setCharacterEncoding("UTF-8");
        //  Solve the problem of responding to Chinese random code 
        resp.setContentType("text/html; charset=UTF-8");

add to cookie, Save in browser ：
In browser applicatioin Item can be viewed .

    protected void createCookie(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    
        //1  establish Cookie object 
        Cookie cookie = new Cookie("key4", "value4");
        //2  Notify the client to save Cookie
        resp.addCookie(cookie);
        //1  establish Cookie object 
        Cookie cookie1 = new Cookie("key5", "value5");
        //2  Notify the client to save Cookie
        resp.addCookie(cookie1);

        resp.getWriter().write("Cookie Create success ");
    }

get cookie

    protected void getCookie(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    
        Cookie[] cookies = req.getCookies();
        for (Cookie cookie : cookies) {
    
            // getName Method returns Cookie Of key（ name ）
            // getValue Method returns Cookie Of value value 
            resp.getWriter().write("Cookie[" + cookie.getName() + "=" + cookie.getValue() + "] <br/>");
        }
        Cookie iWantCookie = CookieUtils.findCookie("key1", cookies);
// for (Cookie cookie : cookies) {
    
// if ("key2".equals(cookie.getName())) {
    
// iWantCookie = cookie;
// break;
// }
// }
        //  If not equal to null, Explain that the given value , That is to find what you need Cookie
        if (iWantCookie != null) {
    
            resp.getWriter().write(" I found what I needed Cookie");
        }
    }

Set up cookie Life time of

• The parameter is an integer , How many seconds does it survive
• Parameter is -1, Then the browser closes ,cookie Delete immediately
• Parameter is 0, Delete immediately

    /** *  Default session level Cookie * * @param req * @param resp * @throws ServletException * @throws IOException */
    protected void defaultLife(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    
        Cookie cookie = new Cookie("defalutLife", "defaultLife");
        cookie.setMaxAge(-1);// Set the time to live 
        resp.addCookie(cookie);
    }

Create with path Of cookie

    protected void testPath(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    
        Cookie cookie = new Cookie("path1", "path1");
        // getContextPath() ===>>>>  Get the engineering path 
        cookie.setPath(req.getContextPath() + "/abc"); // ===>>>> / Project path /abc
        resp.addCookie(cookie);
        resp.getWriter().write(" Created a system with Path The path of Cookie");
    }

Use cookie Login without user name

package com.atguigu.servlet;

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

public class LoginServlet extends HttpServlet {
    

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    
        String username = req.getParameter("username");
        String password = req.getParameter("password");

        if ("wzg168".equals(username) && "123456".equals(password)) {
    
            // Sign in   success 
            Cookie cookie = new Cookie("username", username);
            cookie.setMaxAge(60 * 60 * 24 * 7);// At present Cookie Within one week 
            resp.addCookie(cookie);
            System.out.println(" Sign in   success ");
        } else {
    
//  Sign in   Failure 
            System.out.println(" Sign in   Failure ");
        }
    }
}

Two 、session

establish session

    protected void createOrGetSession(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    
        //  Create and get Session Conversation object 
        HttpSession session = req.getSession();
        //  Judge   At present Session conversation , Whether it is newly created 
        boolean isNew = session.isNew();
        //  obtain Session Unique identification of the session  id
        String id = session.getId();
        resp.getWriter().write(" Got Session, its id yes ：" + id + " <br /> ");
        resp.getWriter().write(" This Session Is it a new creation ：" + isNew + " <br /> ");
    }

towards session Store data in the field

    /** *  Go to Session Save data in  * * @param req * @param resp * @throws ServletException * @throws IOException */
    protected void setAttribute(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    
        req.getSession().setAttribute("key1", "value1");
        resp.getWriter().write(" Has gone to Session Data is saved in ");

    }
    /** *  obtain Session Data in domain  * * @param req * @param resp * @throws ServletException * @throws IOException */
    protected void getAttribute(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    
        Object attribute = req.getSession().getAttribute("key1");
        resp.getWriter().write(" from Session Take out in key1 The data of ：" + attribute);
    }

session The default timeout length in 30mins, You can set

    protected void defaultLife(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    
        //  Got Session Default timeout of 
        int maxInactiveInterval = req.getSession().getMaxInactiveInterval();
        resp.getWriter().write("Session The default timeout of is ：" + maxInactiveInterval + "  second  ");
    }

    protected void life3(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    
        //  First get Session object 
        HttpSession session = req.getSession();
        //  Set up current Session3 Seconds after timeout 
        session.setMaxInactiveInterval(3);
        resp.getWriter().write(" At present Session Has been set to 3 Seconds after timeout ");
    }

Set up session invalid

    protected void deleteNow(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    
        //  First get Session object 
        HttpSession session = req.getSession();
        //  Give Way Session The session is about to time out 
        session.invalidate();
        resp.getWriter().write("Session Has been set to timeout （ Invalid ）");
    }

3、 ... and 、 The browser and Session Technical insider of the relationship

The logic of logout is actually to get the requested session, Then disable it .
req.getSession().invalidate();