Cookie[] cookies = req.getCookies(); //獲得cookie
cookie.getName() //獲得cookie中的鍵
cookie.getValue() //獲得cookie中的值	
new Cookie("LastLoginTime",System.currentTimeMillis()+"") //新建一個(gè)cookie
cookie.setMaxAge(24*60*60); //設(shè)置cookie有效期
resp.addCookie(cookie); //響應(yīng)給客戶(hù)端一個(gè)cookie

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    //解決中文亂碼
    req.setCharacterEncoding("utf-8");
    resp.setCharacterEncoding("utf-8");
    resp.setContentType("text/html; charset=utf-8");
    PrintWriter out = resp.getWriter();
    Cookie[] cookies = req.getCookies();
    //判斷cookie是否存在
    if(cookies == null){
        out.println("第一次訪問(wèn)網(wǎng)站");
    }else{
        out.write("您上一次訪問(wèn)的時(shí)間是：");
        for (Cookie cookie : cookies) {
            if("LastLoginTime".equals(cookie.getName())){
                //獲取cookie中的值
                long time = Long.parseLong(cookie.getValue());
                Date date = new Date(time);
                DateFormat dfd = DateFormat.getDateInstance(DateFormat.MEDIUM,Locale.CHINA);
                DateFormat dft = DateFormat.getTimeInstance(DateFormat.MEDIUM, Locale.CHINA);
                out.write(dfd.format(date)+dft.format(date));
            }
        }
    }
    Cookie cookie = new Cookie("LastLoginTime",System.currentTimeMillis()+"");
    //設(shè)置cookie有效期為一天
    cookie.setMaxAge(24*60*60);
    resp.addCookie(cookie);
}

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    //解決亂碼
    req.setCharacterEncoding("utf-8");
    resp.setCharacterEncoding("utf-8");
    resp.setContentType("text/html; charset=utf-8");
    PrintWriter out = resp.getWriter();
    //得到Session
    HttpSession session = req.getSession();
    //給session中存東西
    session.setAttribute("name",new Person("張三",18));
    //獲取session的id
    String id = session.getId();
    //判斷session是不是新創(chuàng)建的
    if(session.isNew()){
        out.write("session創(chuàng)建成功，ID:"+id);
    }else{
        out.write("session已經(jīng)存在，id："+id);
    }
    //Session創(chuàng)建的時(shí)候做了什么事
    //        Cookie jsessionid = new Cookie("JSESSIONID", id);
    //        resp.addCookie(jsessionid);
}
//Person類(lèi)
public class Person {
    private String name;
    private int age;
    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
    public Person() {
    }
    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
}

//得到Session
HttpSession session = req.getSession();
Person name = (Person) session.getAttribute("name");
System.out.println(name);

//得到Session
HttpSession session = req.getSession();
session.removeAttribute("name");
//注銷(xiāo)session
session.invalidate();

<!--    設(shè)置Session的默認(rèn)失效時(shí)間-->
    <session-config>
<!--        15分鐘后session自動(dòng)失效，以分鐘為單位-->
        <session-timeout>15</session-timeout>
    </session-config>