Session (emphasis)
What is Session:
-
The server will create a Session object for each user (browser)
-
A session occupies a browser, as long as the browser is not closed, the session will exist
-
After the user logs in, the entire website can be accessed! –> Save user information; save shopping cart information...
The difference between Session and cookie:
- Cookie is to write the user's data to the user's browser, and the browser saves it (you can save multiple)
- Session writes the user's data to the user's exclusive session and saves it on the server side (saves important information to reduce waste of server resources)
- Session object is created by the server
scenes to be used:
- Save the information of a logged-in user
- Shopping cart information
- Data that is frequently used throughout the website, we save it in the Session
Use Session:
public class SessionDemo01 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//解决乱码问题
req.setCharacterEncoding("UTF-8");
resp.setCharacterEncoding("UTF-8");
resp.setContentType("text/html;charset=utf-8");
//得到Session
HttpSession session = req.getSession();
//给Session中存东西
session.setAttribute("name",new Person("家明","1"));
//获取Session的ID
String sessionId = session.getId();
//判断Session是不是新创建
if (session.isNew()){
resp.getWriter().write("Session创建成功,ID:"+sessionId);
}else {
resp.getWriter().write("Session已经在服务器中存在了,ID:"+sessionId);
}
//Session创建的时候做了什么事情；
// Cookie cookie = new Cookie("JSESSIONID",sessionId);
// resp.addCookie(cookie);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
//得到Session
HttpSession session = req.getSession();
Person person = (Person) session.getAttribute("name");
System.out.println(person.toString());
HttpSession session = req.getSession();
session.removeAttribute("name");
//手动注销Session
session.invalidate();
The session automatically expires (configured in web.xml):
<!--设置Session默认的失效时间-->
<session-config>
<!--15分钟后Session自动失效，以分钟为单位-->
<session-timeout>15</session-timeout>
</session-config>
