Session

服务器会给每一个用户（浏览器）创建一个Session对象

打开浏览器会创建一个sessionID，关闭浏览器则session失效

注意

Session里面的东西存放在Web服务器中，用户拿到的是SessionID！！！

SessionID是每个用户唯一的

Session是用户级的，Application（ServletContext）是应用级的

代码示例

SessionTest.java

import javax.servlet.ServletException;
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 SessionTest extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //解决中文乱码问题
        req.setCharacterEncoding("UTF-8");
        resp.setCharacterEncoding("UTF-8");
        resp.setHeader("content-type","text/html;charset=UTF-8");

        //得到Session
        HttpSession session = req.getSession();

        //给Session中存东西
        session.setAttribute("name","马赫666");

        //获取Session的ID
        String id = session.getId();

        //判断Session是不是新创建的
        if (session.isNew()){
            resp.getWriter().println("session创建成功，ID="+id);
        }else{
            resp.getWriter().println("session已经存在，ID="+id);
        }

        //获取Session中的内容
        //String name = (String) session.getAttribute("name");
        //System.out.println(name);

        //注销Session
        //session.invalidate();

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

配置Session的有效时间

web.xml

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
				http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0"
         metadata-complete="true">

    <servlet>
        <servlet-name>sTest</servlet-name>
        <servlet-class>com.mahe666.servlet.SessionTest</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>sTest</servlet-name>
        <url-pattern>/sTest</url-pattern>
    </servlet-mapping>

    <session-config>
        <!--代表一分钟后过期-->
        <session-timeout>1</session-timeout>
    </session-config>

</web-app>

Session销毁

只有两种销毁方法

1. 调用invalidate手动销毁
2. 配置有效时间