public void setMaxInactiveInterval(int interval) 设置 Session 的超时时间(以秒为单位),超过指定的时长,Session 就会被销毁。
值为正数的时候,设定 Session 的超时时长。
负数表示永不超时
public int getMaxInactiveInterval()获取 Session 的超时时间
public void invalidate() 让当前 Session 会话立即无效
如果没有调用 setMaxInactiveInterval() 来指定 Session 的生命时长,Tomcat 会以 Session默认时长为准,Session 默认的超时为 30 分钟, 可以在 tomcat 的 web.xml 设置
Session 的生命周期指的是 :客户端/浏览器两次请求最大间隔时长,而不是累积时长。即当客户端访问了自己的 session,session 的生命周期将从 0 开始重新计算。(解读: 指的是同一个会话两次请求之间的间隔时间)
底层: Tomcat 用一个线程来轮询会话状态,如果某个会话的空闲时间超过设定的最大值,则将该会话销毁
public class CreateSession2 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("CreateSession2 被调用");
//创建session
HttpSession session = request.getSession();
System.out.println("CreateSession2 sid= " + session.getId());
//设置生命周期为 60s
session.setMaxInactiveInterval(60);
session.setAttribute("u", "jack");
//回复一下浏览器
response.setContentType("text/html;charset=utf-8");
PrintWriter writer = response.getWriter();
writer.println("创建session成功, 设置生命周期60s
");
writer.flush();
writer.close();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
public class ReadSession2 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//System.out.println("ReadSession2 被调用...");
//1. 获取到session
HttpSession session = request.getSession();
System.out.println("ReadSession2 sid= " + session.getId());
//2. 读取session的属性
Object u = session.getAttribute("u");
if (u != null) {
System.out.println("读取到session属性 u= " + (String) u);
} else {
System.out.println("读取不到session属性 u 说明原来的session被销毁");
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
指的是两次访问 session 的最大间隔时间
如果你在 session 没有过期的情况下,操作 session, 则会重新开始计算生命周期
session 是否过期,是由服务器来维护和管理
如我们调用了 invaliate() 会直接将该 session 删除/销毁
如果希望删除 session 对象的某个属性, 使用 removeAttribu(“xx”)
public class DeleteSession extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("DeleteSession 被调用...");
//演示如何删除session
HttpSession session = request.getSession();
session.invalidate();
// 如果你要删除session的某个属性
//session.removeAttribute("xxx");
//回复一下浏览器
response.setContentType("text/html;charset=utf-8");
PrintWriter writer = response.getWriter();
writer.println("删除session成功
");
writer.flush();
writer.close();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
只要密码为 666666, 我们认为就是登录成功
如果验证成功,则进入管理页面 ManageServelt.java ,否则进入 error.html
如果用户直接访问 ManageServet.java , 重定
DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>登录页面title>
head>
<body>
<h1>用户登录界面h1>
<form action="/cs/loginCheck" method="post">
u:<input type="text" name="username"><br/>
p:<input type="password" name="pwd"><br/>
<input type="submit" value="登录">
form>
body>
html>
public class LoginCheckServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("LoginCheckServlet 被调用..");
//功能-> 自己拆解 -> 逐步实现
//1. 得到提交的用户名和密码
String username = request.getParameter("username");
String password = request.getParameter("password");
if("666666".equals(password)) {//认为合法
//把用户名保存到 session
HttpSession session = request.getSession();
session.setAttribute("loginuser", username);
//请求转发到ManageServlet
request.getRequestDispatcher("/manage").forward(request, response);
} else {
//请求转发进入到 error.html
request.getRequestDispatcher("/error.html").forward(request, response);
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
public class ManageServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//判断该用户是否登录过
HttpSession session = request.getSession();
Object loginuser = session.getAttribute("loginuser");
if(loginuser == null) {//说明该用户没有登录
//重新登录-> 请求重定向
//response.sendRedirect("/cs/userlogin.html");
response.sendRedirect(request.getContextPath() + "/userlogin.html");
return;
} else {
response.setContentType("text/html;charset=utf-8");
PrintWriter writer = response.getWriter();
writer.println("用户管理页面
");
writer.println("欢迎你, 管理员:" + loginuser.toString());
writer.flush();
writer.close();
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>登录失败title>
head>
<body>
<h1>登录失败h1>
<a href="/cs/userlogin.html">点击重新登录a>
body>
html>