狂神说Java Web学习笔记_Session

原理图

服务器会给每一个用户（浏览器）创建一个session对象

一个session独占一个浏览器，主要浏览器没有关，这个session就存在

登录之后，整个网站都可以访问

常用场景

保存一个用户的登录信息

在整个网站中经常会使用到的数据

常用的session方法

//得到Session
HttpSession session = req.getSession();
//给Session中存数据
session.setAttribute("name","admin");
//获取Session中的数据
session.getAttribute("name");
//删除Session中的数据
session.removeAttribute("name");
//获取Session的ID
String sessionId = session.getId()
//手动注销Session
Sessionsession.invalidate();

Sessiondemo03

手动注销session invalidate

另一种方式，web.xml设置默认的注销时间

Session-timeout

cookie设置超时

应用

使用Session存储字符串

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

public class SessionDemo01 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws 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();
        String id = session.getId();

        //给session中存入字符串
        session.setAttribute("name", "闹闹");
        String name = (String) session.getAttribute("name");
        resp.getWriter().write("获取到的sessionId为：" + id + ", 获取到的name属性的值为：" + name);
    }
}

<servlet>
    <servlet-name>sessionDemo01</servlet-name>
    <servlet-class>com.dawn.session.SessionDemo01</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>sessionDemo01</servlet-name>
    <url-pattern>/sessionDemo01</url-pattern>
</servlet-mapping>

不同浏览器获取到的SessionId值不一样

使用Session存储对象

import com.dawn.entity.Person;

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

public class SessionDemo02 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws 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();
        String id = session.getId();

        //给session中存入对象
        Person person = new Person("bambi", 26);

        session.setAttribute("person", person);
        Person personGet = (Person) session.getAttribute("person");
        resp.getWriter().write("获取到的sessionId为：" + id + ", 获取到的person对象的内容为：" + personGet.toString());
    }
}

<servlet>
    <servlet-name>sessionDemo02</servlet-name>
    <servlet-class>com.dawn.session.SessionDemo02</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>sessionDemo02</servlet-name>
    <url-pattern>/sessionDemo02</url-pattern>
</servlet-mapping>

手动注销Session

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

public class SessionDemo03 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        req.setCharacterEncoding("utf-8");
        resp.setCharacterEncoding("utf-8");
        resp.setContentType("text/html;charset=utf-8");

        HttpSession session = req.getSession();
        session.invalidate();
        resp.getWriter().write("设置session失效成功");
    }
}

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

public class SessionDemo01 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws 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();
        String id = session.getId();
        if (session.isNew()) {
            resp.getWriter().write("session创建成功，id为: " + id);
        } else {
            resp.getWriter().write("session在服务器中已经存在，无需再次创建，对应id为: " + id);
        }
    }
}

<servlet>
    <servlet-name>sessionDemo03</servlet-name>
    <servlet-class>com.dawn.session.SessionDemo03</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>sessionDemo03</servlet-name>
    <url-pattern>/sessionDemo03</url-pattern>
</servlet-mapping>

调用注销session的servlet接口之前，可以获取到session

紧接着调用注销session接口

再次访问获取session接口，发现已经重新生成了一个新的session，之前的那个已经被注销了

设置Session自动过期

<!--设置Session默认的失效时间-->
<session-config>
    <!--1分钟后Session自动失效，以分钟为单位-->
    <session-timeout>1</session-timeout>
</session-config>

访问sessionDemo01接口

预期1分钟之后再次访问这个接口的时候，应该重新生成一个新的sessionId